ynchuan / blog-ynchuan Goto Github PK

var obj = {
    a: 'obja',
    b: 'objb',
    c: 'objc',
    d: 'objd',
};
var arr = ['arr1', 'arr2', 'arr3', 'arr4'];

for (var key in obj) {
    console.log(key);
    console.log("====" + obj[key]);
}

for (var key in arr) {
    console.log(key);
    console.log("====" + arr[key]);
}

for (var key of arr) {
    console.log(key);
}

for (var key of obj) { //报错，没有继承iterator
    console.log(key);
}

/**
 * 函数节流（throttle）：某个动作规定的时间内只执行第一次
 */

const throttle = (action, idle) => {
    let last = 0;
    return (...prop) => {
        let curr = +new Date;
        if (curr - last > idle) {
            action.apply(this, prop);
            last = curr;
        }
    }
};

const throttleAction = throttle((...prop) => {
    console.log(prop);
}, 1000);

throttleAction('throttle1');
throttleAction('throttle2');
throttleAction('throttle3'); // 输出 throttle1

setTimeout(() => {
    throttleAction('throttle4');
    throttleAction('throttle5');
    throttleAction('throttle6'); // 输出 throttle4
}, 2000);


/**
 * 函数防抖 （debounce）：某个动作规定的时间内只执行最后一次
 */

const debounce = (action, idle) => {
    let handler;
    return (...prop) => {
        handler && clearTimeout(handler);
        handler = setTimeout(() => {
            action.apply(this, prop);
        }, idle);
    }
};

const debounceAction = debounce((...prop) => {
    console.log(prop);
}, 1000);

debounceAction('debounce1');
debounceAction('debounce2');
debounceAction('debounce3'); // 输出 debounce3

setTimeout(() => {
    debounceAction('debounce4');
    debounceAction('debounce5');
    debounceAction('debounce6'); // 输出 debounce6
}, 2000);

/**
 * 由于map具有有序性和一一映射的特性，所以map可以转换为数组和对象
 * map->array 二维数组形式，可逆
 * map->object 键值对形式，可逆
 */


let mapToObj = (map) => {
    let obj = Object.create(null);
    for ([key, value] of map.entries()) {
        obj[key] = value;
    }
    return obj;
}

let map = new Map();
map.set('a', 'a').set('c', 1).set({}, {}).set([1, 2], [3, 4]);
console.log("map to object test:");
console.log(mapToObj(map));


let objToMap = (obj) => {
    let ret = new Map;
    for (let key in obj) {
        ret.set(key, obj[key]);
    }
    return ret;
};

let obj = { 'a': 1, '2': 'b' };
console.log("object to map test:");
console.log(objToMap(obj));


let arrToMap = (arr) => {
    return new Map(arr);
};
let arr = [
    [1, 'a'],
    [2, 'b'],
    [4, 'd']
];
console.log("array to Map test:");
console.log(arrToMap(arr));


let mapToArr = (map) => {
    return [...map];
};
console.log("map to array test:");
console.log(mapToArr(new Map().set('a', 'a').set('c', 1).set({}, {}).set([1, 2], [3, 4])));



let jsonToMap1 = (json) => {
    return objToMap(JSON.parse(json));
};
let jsonToMap2 = (json) => {
    return new Map(JSON.parse(json));
};
let json1 = '{"a":"a","b":"b"}';
console.log("json to map test 1:");
console.log(jsonToMap1(json1));

let json2 = '[["a","1"],["b"],[3,"c"]]';
console.log("json to map test 2:");
console.log(jsonToMap2(json2));




let mapToJson = (map) => {
    return JSON.stringify(mapToObj(map));
};
console.log("map to array json:");
console.log(mapToJson(new Map().set('a', 'a').set('c', 1).set({}, {}).set([1, 2], [3, 4])));