ES6中數(shù)組array新增方法實例總結(jié)

let arr=[1,2,234,'sdf',-2];
arr.find(function(x){
 return x<=2;
})//結(jié)果：1，返回第一個符合條件的x值
arr.find(function(x,i,arr){
 if(x<2){console.log(x,i,arr)}
})//結(jié)果：1 0 [1, 2, 234, "sdf", -2]，-2 4 [1, 2, 234, "sdf", -2]

let arr=[1,2,234,'sdf',-2];
arr.findIndex(function(x){
 return x<=2;
})//結(jié)果：0，返回第一個符合條件的x值的索引
arr.findIndex(function(x,i,arr){
 if(x<2){console.log(x,i,arr)}
})//結(jié)果：1 0 [1, 2, 234, "sdf", -2]，-2 4 [1, 2, 234, "sdf", -2]

let arr=[1,2,234,'sdf',-2];
arr.includes(2);// 結(jié)果true，返回布爾值
arr.includes(20);// 結(jié)果：false，返回布爾值
arr.includes(2,3)//結(jié)果：false，返回布爾值

let arr=[1,2,234,'sdf',-2];
for(let a of arr.keys()){
 console.log(a)
}//結(jié)果：0,1,2,3,4 遍歷了數(shù)組arr的索引

let arr=[1,2,234,'sdf',-2];
for(let a of arr.values()){
 console.log(a)
}//結(jié)果：1,2,234,sdf,-2 遍歷了數(shù)組arr的值

let arr=['w','b'];
for(let a of arr.entries()){
 console.log(a)
}//結(jié)果：[0,w],[1,b]
for(let [i,v] of arr.entries()){
 console.log(i,v)
}//結(jié)果：0 w,1 b

let arr=['w','b'];
arr.fill('i')//結(jié)果：['i','i']，改變原數(shù)組
arr.fill('o',1)//結(jié)果：['i','o']改變原數(shù)組,第二個參數(shù)表示填充起始位置
new Array(3).fill('k').fill('r',1,2)//結(jié)果：['k','r','k']，第三個數(shù)組表示填充的結(jié)束位置

Array.of('w','i','r')//["w", "i", "r"]返回數(shù)組
Array.of(['w','o'])//[['w','o']]返回嵌套數(shù)組
Array.of(undefined)//[undefined]依然返回數(shù)組
Array.of()//[]返回一個空數(shù)組

["w", "i", "r"].copyWithin(0)//此時數(shù)組不變
["w", "i", "r"].copyWithin(1)//["w", "w", "i"],數(shù)組從位置1開始被原數(shù)組覆蓋，只有1之前的項0保持不變
["w", "i", "r","b"].copyWithin(1,2)//["w", "r", "b", "b"],索引2到最后的r,b兩項分別替換到原數(shù)組1開始的各項，當(dāng)數(shù)量不夠，變終止
["w", "i", "r",'b'].copyWithin(1,2,3)//["w", "r", "r", "b"]，強(qiáng)第1項的i替換為第2項的r

Array.from({'0':'w','1':'b',length:2})//["w", "b"],返回數(shù)組的長度取決于對象中的length，故此項必須有！
Array.from({'0':'w','1':'b',length:4})//["w", "b", undefined, undefined],數(shù)組后2項沒有屬性去賦值，故undefined
Array.from({'0':'w','1':'b',length:1})//["w"],length小于key的數(shù)目，按序添加數(shù)組

let divs=document.getElementsByTagName('div');
Array.from(divs)//返回div元素數(shù)組
Array.from('wbiokr')//["w", "b", "i", "o", "k", "r"]
Array.from([1,2,3],function(x){
 return x+1})//[2, 3, 4],第二個參數(shù)為回調(diào)函數(shù)