将对象推入javascript深拷贝还是浅拷贝中的数组？

Question

相当不言自明的问题...当在 javascript 中的数组上使用 .push() 时，推入数组的对象是指针（浅）还是实际对象（深）不管输入。

Answer 1

这取决于你要推动什么。对象和数组作为指向原始对象的指针被推送。内置的原始类型（如数字或布尔值）作为副本推送。因此，由于对象不会以任何方式复制，因此它们没有深拷贝或浅拷贝。

这是一个显示它的工作 sn-p：

var array = [];
var x = 4;
let y = {name: "test", type: "data", data: "2-27-2009"};

// primitive value pushes a copy of the value 4
array.push(x);                // push value of 4
x = 5;                        // change x to 5
console.log(array[0]);        // array still contains 4 because it's a copy

// object reference pushes a reference
array.push(y);                // put object y reference into the array
y.name = "foo";               // change y.name property
console.log(array[1].name);   // logs changed value "foo" because it's a reference    

// object reference pushes a reference but object can still be referred to even though original variable is no longer within scope
if (true) {
    let z = {name: "test", type: "data", data: "2-28-2019"};
    array.push(z);
}

console.log(array[2].name);   // log shows value "test" since the pointer reference via the array is still within scope

Answer 2

jfriend00 在这里是正确的，但需要澄清一点：这并不意味着您不能更改变量指向的内容。也就是说，y 最初引用了您放入数组中的某个变量，但是您可以获取名为 y 的变量，将其与现在数组中的对象断开连接，然后连接 y（即 让它引用）完全不同的东西不改变现在只被数组引用的对象。

http://jsfiddle.net/rufwork/5cNQr/6/

var array = [];
var x = 4;
var y = {name: "test", type: "data", data: "2-27-2009"};

// 1.) pushes a copy
array.push(x);
x = 5;
document.write(array[0] + "<br>");    // alerts 4 because it's a copy

// 2.) pushes a reference
array.push(y);
y.name = "foo";

// 3.) Disconnects y and points it at a new object
y = {}; 
y.name = 'bar';
document.write(array[1].name + ' :: ' + y.name + "<br>");   
// alerts "foo :: bar" because y was a reference, but then 
// the reference was moved to a new object while the 
// reference in the array stayed the same (referencing the 
// original object)

// 4.) Uses y's original reference, stored in the array,
// to access the old object.
array[1].name = 'foobar';
document.write(array[1].name + "<br>");
// alerts "foobar" because you used the array to point to 
// the object that was initially in y.