四十六.字符串的方法

1.增加

1.1 concat 拼接

var a = 'hello'
var b = "world"
console.log(a.concat(b));

2. 查询

2.1 slice(startIndex,endIndex)

2.2 substr(index,length)

注意：第二个参数 为长度

2.3 substring(startIndex,endIndex)

var arr = "hello"
console.log(arr.slice(0)); // hello
console.log(arr.slice(0,3)); // hel
console.log(arr.substr(0,3)); // hel
console.log(arr.substring(0,2)); // he

2.4 charAt(index) 根据下标查找对应的值

var str = "hello"
console.log(str.charAt(1)); // e

2.5 indexOf(value) 根据值查找对应的下标

var arr = "hello";
console.log(arr.indexOf('e')); // 1

2.6 includes 是否包含某位(多位)字符

var arr = "hello"
console.log(arr.includes("eh")); //false

3. length 字符串的长度

var str = "hello"
console.log(str.length);
var s = "故事的结尾，心上人"
console.log(handleStr(s));
function handleStr(value){
  if(value.length>5){
    return value.slice(0,5)+"..."
  }
  return value
}