对象是否在 javascript 深拷贝或浅拷贝中推入数组? [英] Do objects pushed into an array in javascript deep or shallow copy?

问题描述

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)不管类型.

Pretty self evident question...When using .push() on an array in javascript, is the object pushed into the array a pointer (shallow) or the actual object (deep) regardless of type.

推荐答案

这取决于你在推动什么.对象和数组作为指向原始对象的指针推送.数字或布尔值等内置原始类型作为副本推送.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.

It depends upon what you're pushing. Objects and arrays are pushed as a pointer to the original object . Built-in primitive types like numbers or booleans are pushed as a copy. So, since objects are not copied in any way, there's no deep or shallow copy for them.

这是一个显示它的工作片段:

Here's a working snippet that shows it:

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

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