# 数组

let arr = [1,2,3,4,5]
let a = 2;
// 判断 value 是否存在于 数组中
function array_has (array,value) {
	for(let i = 0; i < array.length; i++) {
		if(array[i] === val) return;
	}
	return - 1;
}

if(array_has(arr,a) > -1) {
	arr.splice(index,1);
}

let arr = [1,2,3,4,5,2,3];
let newArr = Array.from(new Set(arr));

// 也可以这样
let newArr = [...new Set(arr)];