1.数组 shift unshift pop push
头删增 尾删增
// 数组 shift unshift pop push
var str="a,b,c,d,e,f";
var arr=str.split(",");
console.log("arr: "+arr);
var shift1=arr.shift();
console.log("shift1: "+shift1); //返回删除的数组第一个元素 a
console.log("arr: "+arr); // b c d e f
var unshift1=arr.unshift('aa');
console.log("unshift1: "+unshift1); // 返回长度 6
console.log("arr: "+arr); // 数组头部添加 aa b c d e f var pop1=arr.pop();
console.log("pop1: "+pop1); // 返回删除的数组最后一个元素 f
console.log("arr: "+arr); // aa b c d e var push1=arr.push("ff");
console.log("push1: "+push1); // 返回长度 6
console.log("arr: "+arr); // aa b c d e ff
2.string chatAt() indexOf() split() substr()
array join() reverse()
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
<style>
p{line-height: 40px;
border-bottom: 1px solid green;}
</style>
</head> <body> string chatAt() indexOf() split() substr()
<script>
var str='hello';
console.log("chartAt(): "+str.charAt(0)); // e // 根据索引返回 char 字符
console.log("indexOf(): "+str.indexOf('e')); //1 // 根据字符返回 index 索引
var arr = str.split('');
for(let i of arr){
console.log("split(): "+i); // split 转成数组
}
var str2=str.substr(0,3);
console.log("substr(): "+str2); // hel 截取字符串
</script>
array shift() unshift() pop() push() join() reverse()
<script>
var arr2=['a','b','c','d'];
var str3=arr2.join(''); // 用空格连接
console.log("join(): "+str3);
var str4=arr2.reverse().join('');
console.log("reverse(): "+str4);
</script> <script>
function unique(arr) {
let obj = {};
let data =[];
for(let i =0,l=arr.length;i<l;i++){
if(!obj[arr[i]]){
obj[arr[i]]=true;
data.push(arr[i]);
}
}
return data;
}
var arr4=[11,12,13,13,14,15,16,16,17];
console.log("arr4: "+unique(arr4));
</script>
</body>
</html>