JS 删除数组中某个元素

//删除红色的元素  splice（下标，长度）
var arr = ['a','b','c','d'];
arr.splice(1,1);
console.log(arr); 
//['a','c','d']; 
var arr2 = ['a','b','c','d']
arr2.splice(1,2);
console.log(arr2);
//['a','d']