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To talk about the copy of JavaScript, you have to talk about value passing and reference passing in javascript.

There is no specific syntax in javascript to specify which parameters are passed by reference, while other languages do, such as ref in C# and & in PHP.

This is also one of the many disadvantages of javascript.

Let's take a look at the following code:

/ / value pass var I = 3 var j = I * * j = 4; [xss_clean] (I); / / 3Accord / reference pass var m = [1]; var n = m * n [0] = 2; [xss_clean] (n [0]); / / 2

Note that only simple types in javascript are value passing, while other complex types such as arrays and objects are passed by reference by default.

What if we need to copy an object? You must define the method yourself:

/ / Deep copy function, in fact, the value is passed function cloneObject (srcobj) {var tarobj=new Object (); for (var key in srcobj) {/ / determines whether the object tarobj [key] = typeof srcobj [key] = = 'object'?cloneObject (srcobj [key]): srcobj [key];} return tarobj } / / verify the use of the deep copy function / / Test case: var srcObj = {a: 1, b: {b1: ["hello", "hi"], b2: "JavaScript"}}; var abObj = srcObj;// reference passing var tarObj = cloneObject (srcObj); srcObj.a = 2transfersrcObj.b.b1 [0] = "Hello"; console.log (abObj.a); / / 2console.log (abObj.b.b1 [0]) / / Hello, indicating that normal = is a kind of reference passing console.log (tarObj.a); / / 1console.log (tarObj.b.b1 [0]); / / "hello", indicating that the deep copy we defined is value passing

In fact, by instantiating a new object, it opens up a new memory space in the heap so that the variable name in the stack points to the new content in the heap.

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