总结一下JS数组、字符串的方法

var arr = [];
var arr = new Array();
var arr = new Array(10);
var arr = new Array(1, 2);

var arr = [1, 2, 3, 4];
// 增
arr.push(5);
arr.unshift(0);

// 删
arr.pop(5);
arr.shift(0);

// 多操作
array.splice(start)
array.splice(start, deleteCount)
array.splice(start, deleteCount, item1, item2, ...)

arr.splice(0, 0, -1, -2);
arr.splice(0, 1);
arr.splice(3, 0, -4);

var str = '1 2 3 4';
var arr = str.split(' ');
var str1 = arr.join(', ');

var arr1 = [5];
arr1.concat(arr);

arr.indexOf(1);
arr.lastIndexOf(1);

arr.reverse();
arr.sort();

arr.reduce();
arr.reduceRight();

arr.forEach( (item, index) => {
// ...
});

arr.map( (item, index) => {
// ...
});

arr.filter( (item, index) => {
// ...
});

arr.some();
arr.every();