js 案例

1、复杂数组去重

let arr = [
    { name: 'atom',age: '15'},
    { name: 'aili',age:'16'},
    { name:'atom',age:'18'},
    { name: 'aili', age: '16'}
]

function removeRepeatArray(arr) {
    let unique = {};
    arr.forEach(key => {
            unique[JSON.stringify(key)] = key;
    });
    arr = Object.keys(unique).map(data => JSON.parse(data));
    return arr;
}
console.log(removeRepeatArray(arr))
// [
//    { name: 'atom',age: '15'},
//    { name: 'aili',age:'16'},
//    { name:'atom',age:'18'},
//]

2、1+2+3....+100之和

let i=0,item,n=100,sum;
sum = (1+ n) *n / 2;
console.log(sum)  //5050

 3、数组重复个数

let arr = ['apple','orange', 'pear', 'apple', 'orange']
 function getWordCnt () {
     return arr.reduce(function(prev, next){
         prev[next] = (prev[next] + 1) || 1
         return prev;
     },{})
 }
 console.log(getWordCnt()) //{apple: 2, orange: 2, pear: 1}

 4、数据类型检测

 function classOf(obj) {
     if (obj === null) return "Null";
     if (obj === undefined) return 'Undefined';
     return Object.prototype.toString.call(obj).slice(8, -1);
 }