时间不在于你拥有多少，而在于你怎样使用 ------LOL艾克
appetizer：奇怪的JS
const a = ("b"+"a"+ +"a"+"a").toLowerCase()
console.log(a) // banana
start
官方释义MDN
Object.entries():方法返回一个给定对象自身可枚举属性的键值对数组，其排列与使用for...in语句以任意顺序遍历一个对象的除Symbol以外的可枚举属性。") 循环遍历该对象时返回的顺序一致（区别在于 for-in 循环还会枚举原型链中的属性）。(ES7)
Object.fromEntries(): 方法把键值对列表转换为一个对象。(ES10)
Object.entries例子
// 转换
console.log(Object.entries({ name: 'JAY', age: 41 }));
//[ [ 'name', 'JAY' ], [ 'age', 41 ] ]
console.log(Object.entries([1,2,3,4]))
//[ [ '0', 1 ], [ '1', 2 ], [ '2', 3 ], [ '3', 4 ] ]
console.log(Object.entries('banana'))
//[ [ '0', 'b' ],[ '1', 'a' ],[ '2', 'n' ],[ '3', 'a' ],[ '4', 'n' ],[ '5', 'a' ] ]
console.log(Object.entries(1)) //传入数字和浮点数返回 []
// 将OBject 转换为map
const obj = { name: 'JAY', age: 41 };
const map = new Map(Object.entries(obj))
console.log(map)
// Map { 'name' => 'JAY', 'age' => 41 }
Object.fromEntries 列子
// node v10.16.3环境还未有支持，请在谷歌49+版本呢调试
// 转化map
const map = new Map([
['name','周杰伦'],['age',36],
])
console.log(Object.fromEntries(map))
// {name: "周杰伦", age: 36}
// 转化array
const arr = [
['0', 'a'],
['1', 'b'],
['2', 'c']
];
console.log(Object.fromEntries(arr))
// {0: "a", 1: "b", 2: "c"}
// 将对象中的属性数值统一*n
const obj1 = {a:1,b:2,c:3,d:'isD'}
const obj2 = Object.fromEntries(
Object.entries(obj1).map(([key,val])=>{
if(typeof val === 'number')return [key,val*2]
else return [key,val]
})
)
console.log(obj2)
//{a: 2, b: 4, c: 6, d: "isD"}
// format url
const str = "age=zhoujielun&&name=16"
const ar = new URLSearchParams(str)
console.log(Object.fromEntries(ar))
//{age: "zhoujielun", name: "16"}
API MDN地址
API兼容性
Object.fromEntries
Object.entries
URLSearchParams
简易实现
Object.entries
const entries = (inArg)=>{
if(Array.isArray(inArg)){
return inArg.map((x,index)=>[`${index}`,x])
}
if(Object.prototype.toString.call(inArg) === `[object Object]`){
return Object.keys(inArg).map(y=>[y,inArg[y]])
}
if(typeof inArg === 'number')return []
throw 'Cannot convert argument to object'
}
// test
console.log(entries(1))
// []
console.log(entries([1,2,3]))
// [ [ '0', 1 ], [ '1', 2 ], [ '2', 3 ] ]
console.log(entries({age:12,name:'ysss'}))
// [ [ 'age', 12 ], [ 'name', 'ysss' ] ]
if(!Object.entries)Object.entries = entries;
Object.fromEntries
const fromEntries = (arrArg)=>{
// Map
if (Object.prototype.toString.call(arrArg) === '[object Map]') {
const resMap = {};
for (const key of arrArg.keys()) {
resMap[key] = arrArg.get(key);
}
return resMap;
}
// array
if(Array.isArray(arrArg)){
const resArr = {}
arrArg.map(([key,value])=>{
resArr[key] = value
})
return resArr
}
throw 'Uncaught TypeError: argument is not iterable';
}
// test
const map = new Map([
['name', '周杰伦'],
['age', 36]
]);
console.log(fromEntries(map));
// {name: "周杰伦", age: 36}
const arr = [
['0', 'a'],
['1', 'b'],
['2', 'c']
];
console.log(fromEntries(arr))
// {0: "a", 1: "b", 2: "c"}
// polyfill
if(!Object.fromEntries)Object.fromEntries = fromEntries
just
昨天没睡好有些慵懒所以开始总结一些小知识，如果有帮助到的请点个👍，谢谢 , 写的匆忙如有错误请指正。
