去除字符串中重复的字符

方法一

function remove(str){
     let result = '';
     for(let i =0;i<str.length;i++){
         let char = str[i];
         if(result.indexOf(char) ==-1){
             result += char;
         }
     }
     return result;
}
let str='hellojavascript';
console.log(remove(str));

方法二

function remove(str){
    let result = [];
    let json = {};
    for(let i =0;i<str.length;i++){
        let char = str[i];
        if(!json[char]){
            result.push(char);
            json[char] = true;
        }
    }
    return result.join('');
}
let str = 'hellojavascript';
console.log(remove(str));

方法三

function remove(str){
	let result = Array.prototype.filter.call(str,function(char,index,arr){
		return arr.indexOf(char) === index;
	});
	return result.join('')
}
let str = 'hellojavascript';
console.log(remove(str));

方法四

function remove(str){
	let set = new Set(str.split(''))
	return [...set].join('');
}
let str = 'hellojavascript';
console.log(remove(str));