1.Array.from特性

var arr=Array.from({
    '0':'ggb',
    '1':'[email protected]',
    'length':2
})

console.log(arr)//[ 'ggb', '[email protected]' ]

var arr=Array.from({
    '0':'ggb',
    '1':'[email protected]',
    'length':2
},function(item,index){
    return index+':'+item
})

console.log(arr)//[ '0:ggb', '1:
 
[email protected]' ]

var set=new Set(['you','me','she'])
console.log(Array.from(set));//[ 'you', 'me', 'she' ]

var arr=new Array(12);
console.log(arr)//[ , , , , , , , , , , ,  ]
var arr2= Array.of(12)
console.log(arr2)//[ 12 ]

var arr=[2,4,6];
var value= arr.find(function(v){
    return true
})
console.log(value); //2

var value2= arr.findIndex(function(value,index,arr){
    return value>3 //1 返回的是索引
})
console.log(value2);
 

var value =arr.find(function(v){
    return Object.is(v,NaN)
})
console.log(value); //NaN

var arr=['one','two','three','four','five','six','seven','eight']
arr.copyWithin(1,5,7)
console.log(arr);//[ 'one', 'six', 'seven', 'four', 'five', 'six', 'seven', 'eight' ]

var arr=['i','love','you']
arr.fill(5)
console.log(arr);
 

var arr=['i','love','you',':','my','baby','girl']
arr.fill(5,2,5)
console.log(arr);//[ 'i', 'love', 5, 5, 5, 'baby', 'girl' ]