数组映射函数不会改变元素 [英] Array map function doesn't change elements

问题描述

在 JavaScript 中，我有一个数组，它是

In JavaScript, I have an array, which is

array = [true, false]

在某些情况下，我试图初始化这个数组

In some cases, I am trying to initialize this array

array.map(item => {
   item = false
})

运行上述代码后，数组没有改变，仍然是[true, false]，所以.map有时不可靠吗?

After running the above code, the array is not changed, it is still [true, false], so is .map not reliable sometimes?

还有一个问题:运行下面的代码后，数组发生了变化.为什么在这种情况下有效?

ONE MORE QUESTION: After running my below code, the array is changed. Why does it work in this case?

let array = [{id:1, checked: false}, {id:2, checked:true}]
array.map(item => {
    item.checked = true
})

数组变成了[{id:1, checked: true}, {id:2, checked:true}]

推荐答案

JavaScript Array map() 方法

JavaScript Array map() Method

*) 使用为每个数组元素调用函数的结果创建一个新数组，并按顺序为数组中的每个元素调用一次提供的函数.

*)creates a new array with the results of calling a function for every array element and it calls the provided function once for each element in an array, in order.

注意:map()方法对没有值的数组元素不执行函数，也不会改变原数组.

Note: map() Method does not execute the function for array elements without values and it does not change the original array.

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