第 151 题：用最简洁代码实现indexOf方法

[libin1991]

[Leader755]

字符串变为数组，用数组方法findIndex去查找。

[lvwxx]

Object.prototype.sIndexOf = function (char) {
  const len = this.length
  for (let i = 0; i < len; i++) {
    if (this[i] === char) {
      return i
    }
  }
  return -1
}

[lishaoxin123]

_indexOf( str , arr ) {
  if(!arr.length) return;
  if(!arr && arr.length < 1) return;
  const toArrary = obj => [].slice.call(obj);
  let result = -1;
  Array.form 
    ? result = Array.from(arr).findIndex(el => el == str)
    : result = toArrary(arr).findIndex(el => el == str)
  return result;
} 
let strData = '123456'
let arrData = [1,2,3];
console.log(_indexOf(1,strData),'strData');
console.log(_indexOf(1,arrData),'arrData');

[lizhongzhen11]

能使用其它数组api？
能的话，嘿嘿嘿：

const indexOf = (arr, val) => {
  return arr.findIndex(item => item === val);
}

[weiweixuan]

这题考点在哪啊，没盖特到 ，难道是有什么特别6的写法吗

[Mrqianl]

function _indexOf(str, reg, fromIndex = 0) { let index = fromIndex; const { length } = str; if (index <= 0) index = 0; if (index >= length) return -1; const arr = str.slice(fromIndex).split(reg); return arr.length > 1 ? arr[0].length + fromIndex : -1 }

[EzrealPrince]

看了一圈怎么没人考虑indexOf的第二个起始参数呢？

[DarthVaderrr]

function indexOf(arr,target,start=0){
     if(start<0) start+=arr.length;
     if(start>=arr.length) return -1;
     for(let i=start;i<arr.length;++i){
        if(arr[i]===target) return i;
  }
  return -1;
}

[x634725355]

function indexOf(str, a, start) {
    start = start == undefined ? 0 : start;
    for (var i = start; i < str.length; i++) {
        if (str[i] == a) {
            return i;
        }
    }
    return -1;
}

[fxxlsc]

function indexOf(str, serchStr, index) {
if(index){
return str.substr(index,).match(serchStr)?str.substr(index,).match(serchStr).index + index :-1
}else{
return str.match(serchStr)?str.match(serchStr).index:-1
}
}

[Peizy]

Array.prototype.myIndexOf = function(item, start = 0) {
const length = this.length;
const startPos = start >= 0 ? start : length + start;
if (start >= length) return -1;
for (let i = startPos; i < length; i++) {
if (this[i] === item) return i;
}
return -1;
};

[YMaster]

看了一圈怎么没人考虑indexOf的第二个起始参数呢？

因为大家都不咋用这个参数，想不起来了呗

[ghost2113]

Object.prototype.MyIndexOf = function(str, from=0){
    let data = this;
    let isArray = Array.isArray(data);
    let isString = Object.prototype.toString.call(data) == '[object String]';
    if (!isArray && !isString) throw new SyntaxError();
    let len = data.length;
    if(from >= len) return -1;
    for(var i = from; i <len; i++){
        if (isString){
            let strLen = str.length;
            if (data.substr(i, i+strLen) == str){
                return i;
            }
        }
        if (isArray && data[i] == str){
            return i;
       }
    }
    return -1;
}