how can I achieve below things in javascript
var parent = {
a: 5,
b: 6
}
var child = parent;
console.log(child.b); // 6
//now if I change the value of b
parent.b = 7
console.log(parent.b); //7
console.log(child.b); //7
//but I want to preserve the previous value of the object property it should not change now.it should show 6 instead of 7 in case of console.log(child.b)
When you do var child = parent both child and parent refer to the same object instance in memory. If you want to copy the property of parent to the child you need to create a new object with the same keys as the parent object.
You can use spread ... or object.assign for this
var parent = {
a: 5,
b: 6
}
var child = {...parent};
var child1 = Object.assign({}, parent);
console.log(child.b); // 6
console.log(child1.b); // 6
//now if I change the value of b
parent.b = 7
console.log(parent.b); //7
console.log(child.b); //6
console.log(child1.b); //6For deep cloning, we need to use other alternatives because
Object.assign()and...copies property values. If the source value is a reference to an object, it only copies that reference value.
Object.assign() instead of ... if it helps.
parent.bnot to affect the value ofchild.b), cloning the object rather than just referring to it is the real problem. The OP's mention of inheritance and such is, I think, a red herring. (Not sure I fully agree with the closure, but I don't disagree enough to unclose it myself, esp. in light of theparent.b/child.bthing. :-) )