diff --git a/src/main/java/me/topchetoeu/jscript/runtime/InstructionRunner.java b/src/main/java/me/topchetoeu/jscript/runtime/InstructionRunner.java
index fe3aeb5..de79882 100644
--- a/src/main/java/me/topchetoeu/jscript/runtime/InstructionRunner.java
+++ b/src/main/java/me/topchetoeu/jscript/runtime/InstructionRunner.java
@@ -94,7 +94,7 @@ public class InstructionRunner {
 
         for (var el : members) {
             var obj = new ObjectValue();
-            obj.defineOwnMember(env, "value", new StringValue(el));
+            obj.defineOwnMember(env, "value", StringValue.of(el));
             frame.push(obj);
         }
 
@@ -137,7 +137,7 @@ public class InstructionRunner {
             case PUSH_NULL: frame.push(Value.NULL); break;
             case PUSH_BOOL: frame.push(BoolValue.of(instr.get(0))); break;
             case PUSH_NUMBER: frame.push(NumberValue.of((double)instr.get(0))); break;
-            case PUSH_STRING: frame.push(new StringValue(instr.get(0))); break;
+            case PUSH_STRING: frame.push(StringValue.of(instr.get(0))); break;
             default:
         }
 
@@ -431,7 +431,7 @@ public class InstructionRunner {
                 res = BoolValue.of(stack[ptr - 1].hasMember(env, stack[ptr], false));
                 break;
             case INSTANCEOF:
-                res = BoolValue.of(stack[ptr - 1].isInstanceOf(env, stack[ptr].getMember(env, new StringValue("prototype"))));
+                res = BoolValue.of(stack[ptr - 1].isInstanceOf(env, stack[ptr].getMember(env, StringValue.of("prototype"))));
                 break;
 
             default: return null;
diff --git a/src/main/java/me/topchetoeu/jscript/runtime/JSONConverter.java b/src/main/java/me/topchetoeu/jscript/runtime/JSONConverter.java
index 714a2b5..a451588 100644
--- a/src/main/java/me/topchetoeu/jscript/runtime/JSONConverter.java
+++ b/src/main/java/me/topchetoeu/jscript/runtime/JSONConverter.java
@@ -19,7 +19,7 @@ import me.topchetoeu.jscript.runtime.values.primitives.numbers.NumberValue;
 public class JSONConverter {
     public static Value toJs(JSONElement val) {
         if (val.isBoolean()) return BoolValue.of(val.bool());
-        if (val.isString()) return new StringValue(val.string());
+        if (val.isString()) return StringValue.of(val.string());
         if (val.isNumber()) return NumberValue.of(val.number());
         if (val.isList()) return ArrayValue.of(val.list().stream().map(JSONConverter::toJs).collect(Collectors.toList()));
         if (val.isMap()) {
diff --git a/src/main/java/me/topchetoeu/jscript/runtime/SimpleRepl.java b/src/main/java/me/topchetoeu/jscript/runtime/SimpleRepl.java
index 5740a3a..2075db9 100644
--- a/src/main/java/me/topchetoeu/jscript/runtime/SimpleRepl.java
+++ b/src/main/java/me/topchetoeu/jscript/runtime/SimpleRepl.java
@@ -97,7 +97,7 @@ public class SimpleRepl {
         res.defineOwnMember(env, "makeSymbol", new NativeFunction(args -> new SymbolValue(args.get(0).toString(args.env))));
         res.defineOwnMember(env, "getSymbol", new NativeFunction(args -> SymbolValue.get(args.get(0).toString(args.env))));
         res.defineOwnMember(env, "getSymbolKey", new NativeFunction(args -> ((SymbolValue)args.get(0)).key()));
-        res.defineOwnMember(env, "getSymbolDescriptor", new NativeFunction(args -> new StringValue(((SymbolValue)args.get(0)).value)));
+        res.defineOwnMember(env, "getSymbolDescriptor", new NativeFunction(args -> StringValue.of(((SymbolValue)args.get(0)).value)));
 
         return res;
     }
@@ -141,7 +141,7 @@ public class SimpleRepl {
                 sb.append(((StringValue)parts[i]).value);
             }
 
-            return new StringValue(sb.toString());
+            return StringValue.of(sb.toString());
         }));
 
         res.defineOwnMember(env, "fromCharCode", new NativeFunction(args -> {
@@ -152,7 +152,7 @@ public class SimpleRepl {
                 sb.append(((StringValue)parts[i]).value);
             }
 
-            return new StringValue(sb.toString());
+            return StringValue.of(sb.toString());
         }));
 
         return res;
@@ -194,7 +194,7 @@ public class SimpleRepl {
             var val = new ArrayValue();
 
             for (var key : args.get(0).getOwnMembers(env, args.get(1).toBoolean())) {
-                val.set(args.env, val.size(), new StringValue(key));
+                val.set(args.env, val.size(), StringValue.of(key));
             }
 
             return val;
@@ -221,8 +221,8 @@ public class SimpleRepl {
             return Value.UNDEFINED;
         }));
         res.defineOwnMember(env, "invokeType", new NativeFunction(args -> {
-            if (((ArgumentsValue)args.get(0)).frame.isNew) return new StringValue("new");
-            else return new StringValue("call");
+            if (((ArgumentsValue)args.get(0)).frame.isNew) return StringValue.of("new");
+            else return StringValue.of("call");
         }));
 
         res.defineOwnMember(env, "invoke", new NativeFunction(args -> {
@@ -249,7 +249,7 @@ public class SimpleRepl {
         res.setPrototype(null, null);
 
         res.defineOwnMember(env, "stringify", new NativeFunction(args -> {
-            return new StringValue(JSON.stringify(JSONConverter.fromJs(env, args.get(0))));
+            return StringValue.of(JSON.stringify(JSONConverter.fromJs(env, args.get(0))));
         }));
         res.defineOwnMember(env, "parse", new NativeFunction(args -> {
             return JSONConverter.toJs(JSON.parse(null, args.get(0).toString(env)));
@@ -260,8 +260,8 @@ public class SimpleRepl {
             return Value.UNDEFINED;
         }));
         res.defineOwnMember(env, "invokeType", new NativeFunction(args -> {
-            if (((ArgumentsValue)args.get(0)).frame.isNew) return new StringValue("new");
-            else return new StringValue("call");
+            if (((ArgumentsValue)args.get(0)).frame.isNew) return StringValue.of("new");
+            else return StringValue.of("call");
         }));
         res.defineOwnMember(env, "invoke", new NativeFunction(args -> {
             var func = (FunctionValue)args.get(0);
diff --git a/src/main/java/me/topchetoeu/jscript/runtime/exceptions/EngineException.java b/src/main/java/me/topchetoeu/jscript/runtime/exceptions/EngineException.java
index ce26c0c..c89314b 100644
--- a/src/main/java/me/topchetoeu/jscript/runtime/exceptions/EngineException.java
+++ b/src/main/java/me/topchetoeu/jscript/runtime/exceptions/EngineException.java
@@ -97,8 +97,8 @@ public class EngineException extends RuntimeException {
 
         if (msg == null) msg = "";
 
-        if (name != null) res.defineOwnMember(Environment.empty(), "name", new StringValue(name));
-        res.defineOwnMember(Environment.empty(), "message", new StringValue(msg));
+        if (name != null) res.defineOwnMember(Environment.empty(), "name", StringValue.of(name));
+        res.defineOwnMember(Environment.empty(), "message", StringValue.of(msg));
         return res;
     }
 
diff --git a/src/main/java/me/topchetoeu/jscript/runtime/values/KeyCache.java b/src/main/java/me/topchetoeu/jscript/runtime/values/KeyCache.java
index 5ab25e5..88be685 100644
--- a/src/main/java/me/topchetoeu/jscript/runtime/values/KeyCache.java
+++ b/src/main/java/me/topchetoeu/jscript/runtime/values/KeyCache.java
@@ -51,7 +51,7 @@ public final class KeyCache {
         this.value = value;
     }
     public KeyCache(String value) {
-        this.value = new StringValue(value);
+        this.value = StringValue.of(value);
         this.stringCache = value;
         this.booleanCache = !value.equals("");
     }
diff --git a/src/main/java/me/topchetoeu/jscript/runtime/values/Value.java b/src/main/java/me/topchetoeu/jscript/runtime/values/Value.java
index 812bd58..1497fb2 100644
--- a/src/main/java/me/topchetoeu/jscript/runtime/values/Value.java
+++ b/src/main/java/me/topchetoeu/jscript/runtime/values/Value.java
@@ -74,8 +74,8 @@ public abstract class Value {
     public static final Key<ObjectValue> GLOBAL = Key.of();
     public static final Key<Map<String, Value>> INTRINSICS = Key.of();
 
-    public static final VoidValue UNDEFINED = new VoidValue("undefined", new StringValue("undefined"));
-    public static final VoidValue NULL = new VoidValue("null", new StringValue("object"));
+    public static final VoidValue UNDEFINED = new VoidValue("undefined", "undefined");
+    public static final VoidValue NULL = new VoidValue("null", "object");
 
     public abstract StringValue type();
     public abstract boolean isPrimitive();
@@ -96,7 +96,7 @@ public abstract class Value {
     }
     public final Value construct(Environment env, String name, Value ...args) {
         var res = new ObjectValue();
-        var proto = getMember(env, new StringValue("prototype"));
+        var proto = getMember(env, StringValue.of("prototype"));
 
         if (proto instanceof ObjectValue) res.setPrototype(env, (ObjectValue)proto);
         else res.setPrototype(env, null);
@@ -395,9 +395,9 @@ public abstract class Value {
                         var curr = supplier.invoke(env, Value.UNDEFINED);
 
                         if (curr == null) { supplier = null; value = null; }
-                        if (curr.getMember(env, new StringValue("done")).toBoolean()) { supplier = null; value = null; }
+                        if (curr.getMember(env, StringValue.of("done")).toBoolean()) { supplier = null; value = null; }
                         else {
-                            this.value = curr.getMember(env, new StringValue("value"));
+                            this.value = curr.getMember(env, StringValue.of("value"));
                             consumed = false;
                         }
                     }
@@ -615,7 +615,7 @@ public abstract class Value {
         b = b.toPrimitive(env);
 
         if (a instanceof StringValue || b instanceof StringValue) {
-            return new StringValue(a.toString(env) + b.toString(env));
+            return StringValue.of(a.toString(env) + b.toString(env));
         }
         else {
             var na = a.toNumber(env);
diff --git a/src/main/java/me/topchetoeu/jscript/runtime/values/functions/FunctionValue.java b/src/main/java/me/topchetoeu/jscript/runtime/values/functions/FunctionValue.java
index fd1aa9d..9714be9 100644
--- a/src/main/java/me/topchetoeu/jscript/runtime/values/functions/FunctionValue.java
+++ b/src/main/java/me/topchetoeu/jscript/runtime/values/functions/FunctionValue.java
@@ -10,8 +10,6 @@ import me.topchetoeu.jscript.runtime.values.primitives.StringValue;
 import me.topchetoeu.jscript.runtime.values.primitives.numbers.NumberValue;
 
 public abstract class FunctionValue extends ObjectValue {
-    private static final StringValue typeString = new StringValue("function");
-
     public String name = "";
     public int length;
     public Value prototype = new ObjectValue();
@@ -21,8 +19,8 @@ public abstract class FunctionValue extends ObjectValue {
 
     private final FieldMember nameField = new FieldMember(this, true, false, false) {
         @Override public Value get(Environment env, Value self) {
-            if (name == null) return new StringValue("");
-            return new StringValue(name);
+            if (name == null) return StringValue.of("");
+            return StringValue.of(name);
         }
         @Override public boolean set(Environment env, Value val, Value self) {
             name = val.toString(env);
@@ -79,7 +77,7 @@ public abstract class FunctionValue extends ObjectValue {
         }
     }
 
-    @Override public StringValue type() { return typeString; }
+    @Override public StringValue type() { return StringValue.of("function"); }
 
     public void setName(String val) {
         if (this.name == null || this.name.equals("")) this.name = val;
diff --git a/src/main/java/me/topchetoeu/jscript/runtime/values/objects/ObjectValue.java b/src/main/java/me/topchetoeu/jscript/runtime/values/objects/ObjectValue.java
index 7c62e1b..b48b1a1 100644
--- a/src/main/java/me/topchetoeu/jscript/runtime/values/objects/ObjectValue.java
+++ b/src/main/java/me/topchetoeu/jscript/runtime/values/objects/ObjectValue.java
@@ -30,8 +30,6 @@ public class ObjectValue extends Value {
         }
     }
 
-    private static final StringValue typeString = new StringValue("object");
-
     protected PrototypeProvider prototype;
 
     public LinkedHashMap<String, Member> members = new LinkedHashMap<>();
@@ -40,14 +38,14 @@ public class ObjectValue extends Value {
     @Override public boolean isPrimitive() { return false; }
     @Override public Value toPrimitive(Environment env) {
         if (env != null) {
-            var valueOf = getMember(env, new StringValue("valueOf"));
+            var valueOf = getMember(env, "valueOf");
 
             if (valueOf instanceof FunctionValue) {
                 var res = valueOf.invoke(env, this);
                 if (res.isPrimitive()) return res;
             }
 
-            var toString = getMember(env, new StringValue("toString"));
+            var toString = getMember(env, "toString");
             if (toString instanceof FunctionValue) {
                 var res = toString.invoke(env, this);
                 if (res.isPrimitive()) return res;
@@ -59,7 +57,7 @@ public class ObjectValue extends Value {
     @Override public String toString(Environment env) { return toPrimitive(env).toString(env); }
     @Override public boolean toBoolean() { return true; }
     @Override public NumberValue toNumber(Environment env) { return toPrimitive(env).toNumber(env);  }
-    @Override public StringValue type() { return typeString; }
+    @Override public StringValue type() { return StringValue.of("object"); }
 
     private State state = State.NORMAL;
 
diff --git a/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/BoolValue.java b/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/BoolValue.java
index 9b09c22..cb963e4 100644
--- a/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/BoolValue.java
+++ b/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/BoolValue.java
@@ -7,11 +7,10 @@ import me.topchetoeu.jscript.runtime.values.primitives.numbers.NumberValue;
 public final class BoolValue extends PrimitiveValue {
     public static final BoolValue TRUE = new BoolValue(true);
     public static final BoolValue FALSE = new BoolValue(false);
-    private static final StringValue typeString = new StringValue("boolean");
 
     public final boolean value;
 
-    @Override public StringValue type() { return typeString; }
+    @Override public StringValue type() { return StringValue.of("boolean"); }
 
     @Override public boolean toBoolean() { return value; }
     @Override public NumberValue toNumber(Environment ext) { return NumberValue.of(value ? 1 : 0); }
@@ -22,7 +21,8 @@ public final class BoolValue extends PrimitiveValue {
     }
 
     @Override public boolean equals(Object other) {
-        if (other instanceof BoolValue bool) return value == bool.value;
+        if (other == this) return true;
+        else if (other instanceof BoolValue bool) return value == bool.value;
         else return false;
     }
 
diff --git a/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/StringValue.java b/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/StringValue.java
index fb32ca4..7409021 100644
--- a/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/StringValue.java
+++ b/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/StringValue.java
@@ -2,6 +2,7 @@ package me.topchetoeu.jscript.runtime.values.primitives;
 
 import java.util.LinkedHashSet;
 import java.util.Set;
+import java.util.WeakHashMap;
 
 import me.topchetoeu.jscript.common.environment.Environment;
 import me.topchetoeu.jscript.common.parsing.Parsing;
@@ -13,10 +14,11 @@ import me.topchetoeu.jscript.runtime.values.objects.ObjectValue;
 import me.topchetoeu.jscript.runtime.values.primitives.numbers.NumberValue;
 
 public final class StringValue extends PrimitiveValue {
-    public final String value;
-    private static final StringValue typeString = new StringValue("string");
+    private static final WeakHashMap<String, StringValue> cache = new WeakHashMap<>();
 
-    @Override public StringValue type() { return typeString; }
+    public final String value;
+
+    @Override public StringValue type() { return of("string"); }
 
     @Override public boolean toBoolean() { return !value.equals(""); }
     @Override public NumberValue toNumber(Environment ext) {
@@ -30,7 +32,8 @@ public final class StringValue extends PrimitiveValue {
     @Override public String toString(Environment ext) { return value; }
 
     @Override public boolean equals(Object other) {
-        if (other instanceof StringValue val) return value.length() == val.value.length() && value.equals(val.value);
+        if (this == other) return true;
+        else if (other instanceof StringValue val) return value.length() == val.value.length() && value.equals(val.value);
         else return false;
     }
 
@@ -61,7 +64,16 @@ public final class StringValue extends PrimitiveValue {
         return res;
     }
 
-    public StringValue(String value) {
+    private StringValue(String value) {
         this.value = value;
     }
+
+    public static StringValue of(String value) {
+        if (cache.containsKey(value)) return cache.get(value);
+        else {
+            StringValue res;
+            cache.put(value, res = new StringValue(value));
+            return res;
+        }
+    }
 }
diff --git a/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/SymbolValue.java b/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/SymbolValue.java
index 5b7c17b..15e96c1 100644
--- a/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/SymbolValue.java
+++ b/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/SymbolValue.java
@@ -10,15 +10,14 @@ import me.topchetoeu.jscript.runtime.values.primitives.numbers.NumberValue;
 
 public final class SymbolValue extends PrimitiveValue {
     private static final HashMap<String, SymbolValue> registry = new HashMap<>();
-    private static final StringValue typeString = new StringValue("symbol");
 
     public final String value;
 
     public Value key() {
-        return registry.containsKey(value) && registry.get(value) == this ? new StringValue(value) : Value.UNDEFINED;
+        return registry.containsKey(value) && registry.get(value) == this ? StringValue.of(value) : Value.UNDEFINED;
     }
 
-    @Override public StringValue type() { return typeString; }
+    @Override public StringValue type() { return StringValue.of("symbol"); }
 
     @Override public boolean toBoolean() { return false; }
     @Override public String toString(Environment env) {
diff --git a/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/VoidValue.java b/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/VoidValue.java
index e54c57a..0949ef3 100644
--- a/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/VoidValue.java
+++ b/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/VoidValue.java
@@ -9,9 +9,9 @@ import me.topchetoeu.jscript.runtime.values.primitives.numbers.NumberValue;
 
 public final class VoidValue extends PrimitiveValue {
     public final String name;
-    public final StringValue typeString;
+    public final String type;
 
-    @Override public StringValue type() { return typeString; }
+    @Override public StringValue type() { return StringValue.of(type); }
     @Override public boolean toBoolean() { return false; }
     @Override public NumberValue toNumber(Environment ext) { return NumberValue.NAN; }
     @Override public String toString(Environment ext) { return name; }
@@ -22,8 +22,8 @@ public final class VoidValue extends PrimitiveValue {
         throw EngineException.ofError(String.format("Cannot read properties of %s (reading '%s')", name, key.toString(env)));
     }
 
-    public VoidValue(String name, StringValue type) {
+    public VoidValue(String name, String type) {
         this.name = name;
-        this.typeString = type;
+        this.type = type;
     }
 }
diff --git a/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/numbers/DoubleValue.java b/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/numbers/DoubleValue.java
index 488961c..183ff49 100644
--- a/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/numbers/DoubleValue.java
+++ b/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/numbers/DoubleValue.java
@@ -25,7 +25,8 @@ public final class DoubleValue extends NumberValue {
     @Override public String toString() { return JSON.stringify(JSONElement.number(value)); }
 
     @Override public boolean equals(Object other) {
-        if (other instanceof NumberValue val) return value == val.getDouble();
+        if (this == other) return true;
+        else if (other instanceof NumberValue val) return value == val.getDouble();
         else return false;
     }
 
diff --git a/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/numbers/IntValue.java b/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/numbers/IntValue.java
index 9b3c74c..0e10367 100644
--- a/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/numbers/IntValue.java
+++ b/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/numbers/IntValue.java
@@ -21,7 +21,8 @@ public final class IntValue extends NumberValue {
 
     @Override public String toString() { return value + ""; }
     @Override public boolean equals(Object other) {
-        if (other instanceof NumberValue val) return val.isLong() && value == val.getLong();
+        if (this == other) return true;
+        else if (other instanceof NumberValue val) return val.isLong() && value == val.getLong();
         else return false;
     }
 
diff --git a/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/numbers/NumberValue.java b/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/numbers/NumberValue.java
index dcab4d9..5060d2f 100644
--- a/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/numbers/NumberValue.java
+++ b/src/main/java/me/topchetoeu/jscript/runtime/values/primitives/numbers/NumberValue.java
@@ -9,9 +9,8 @@ import me.topchetoeu.jscript.runtime.values.primitives.StringValue;
 
 public abstract class NumberValue extends PrimitiveValue {
     public static final NumberValue NAN = new DoubleValue(Double.NaN);
-    private static final StringValue typeString = new StringValue("number");
 
-    @Override public final StringValue type() { return typeString; }
+    @Override public final StringValue type() { return StringValue.of("number"); }
 
     public abstract double getDouble();
     public abstract int getInt();