javascript 杂记

1. 数组杂记

1）数组的判断，使用Array.isArray()

var number = 1;
var arrays = [1, 2, 'number', null];

Array.isArray(number) // false
Array.isArray(arrays)    // true

2）一维数组的深拷贝

// for循环
function copy(arr1, arr2) {
    for (var i  = 0; i < arr1.length; i++) {
        arr2[i] = arr1[i]
     }
}

// slice
var arr1 = [1, 2, 3, 4];
var arr2 = arr1.slice(0);  // 为数组做个副本

// concat
var arr1 = [1, 2, 3, 4];
var arr2 = arr1.concat();

// 扩展运算符...
var arr1 = [1, 2, 3, 4];
var [ ...arr2 ]  = arr1;

3）多维数组的深拷贝

function deepCopy(array) {
    var copy = []
    for (var i = 0; i < array.length; i++) {
        if (array[i]  instanceof Array) {
            copy[i] = deepCopy(array[i])
         } else {
            copy = array[i]
         }
     }
     return copy;
}

4）数组去重

function distinct(array) {
    return [...new Set(array)]
}

var arr = [1, 1, 2, 3, 4, 4, 4];
distinct(arr) // [1, 2, 3, 4]

2. 对象杂记

1）对象的深拷贝

// 扩展运算符...
var obj1 = {
    name: 'Tom',
    age: 10,
    gender: '男'
}
var { ...obj2 } = obj1;