2020-06-17-gaode

1、js里面有哪些数据类型
number boolean string null undefined NaN Symbol
Object Array Map Set

2、null undefined

3、js里面数据的深拷贝如何实现
a.Object.assign()
b.JSON.stringfg(), JSON.parse()
c.递归拷贝

function deepClone (obj) {
var result = {}
var i

if (Object.prototype.toString(obj) === 'Object object') {
    for (i in obj) {
        if (Object.prototype.toString(obj[i]) === 'Object object'){
            result[i] = deepClone(obj[i])
        } else {
            result[i] = obj[i]
        }
    }
}

return result

}

4、promise 和 settimeout，运行的机制有什么区别

setTimeout(function(){console.log(1)},0);
new Promise(function(resolve){
console.log(2)
for( var i=0 ; i<10000 ; i++ ){
i==9999 && resolve()
}
console.log(3)
}).then(function(){
console.log(4)
});
console.log(5);

// 2 3 5 4 1

5、react 组件分为哪些类型、生命周期有哪些

constructor compontWillMount compontDidMount compontWillUpdate compontDidUpdate
compontWillReciveProps compontShouldUpdate compontWillUnmount

getDrived... snap

6、Purecomponent 和 Component区别是什么

Purecomponent 自带compontShouldUpdate 方法的判断

7、redux 单向数据流，由哪些部分组成

action(dispath) reducer Store subScribe

实现按钮点击后，更新“counter” 显示内容加1减1的代码。
<body>
<div id="counter"></div>
<button id="addBtn">+</button>
<button id="minusBtn">-</button>
</body>

var ADD = 'ADD'
var MINUS = 'MINUS'
var counter = 0
var reducer = function (action) {
switch(action){
case ADD:
return counter++
case MINUS:
return counter--
}
}
var Store = {
counter: 0
}

Object.createProperty('counter', Store, {
set: function(){

},
get: function(){
return this.counter
}
})

var val = $('#counter')$ ('#addBtn').on('click', function(){
val.html(reducer(ADD))
})

$('#minusBtn').on('click', function(){
val.html(reducer(MINUS))
})

</script>

8、数组 a、b 合并后并去重
let a = ['a','ab',......];
let b = ['c','cd','a'......]

function (a, b) {
var result

result = Array.from(new Set(a.concat(b)))

return result

}

function quchong (arr) {

// var result = []
var result = {}

// arr.forEach(function(item){
//  if (result.indexOf(item)<0){
//      result.push(item)
//     }
// })

arr.forEach(function(item){
    if (!result[item]){
        result[item] = 1
    }
})

return Object.keys(result)

}

9、react高阶组件，加一个左右10px

class Gaojie extends Componet {
construtor(props){
super(props)
}
render () {
let {child} = this.props
return <div style={{padding: '0 10px'}}><child ...this.props /></div>
}
}