通过 for 循环连接字符串

Question

I'm trying to concatenate strings via for loop but i'm receiving NaNs . What i want to achieve is to get one concatenated string Div #0, Div #1, Div #2, Div #3, .

 var divLength = $('div').length; var str = ''; for(var i=0; i<divLength; i++){ var str =+ "Div #" + [i] + ", "; console.log(str); }

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <div></div> <div></div> <div></div> <div></div>

Answer 1

Don't declare a new str variable inside the loop with var str . Reuse the one you declare outside the loop. Also do +=

 var divLength = $('div').length; var str = ''; for(var i = 0; i < divLength; i++) { str += "Div #" + i + ", "; console.log(str); }

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <div></div> <div></div> <div></div> <div></div>

Answer 2

Besides the selected answer, you could do this with a forEach if you have a list of stuff to put inside those divs :

let string = '';
items.forEach(item => string += '<div>'+ item.description + '</div>');

Answer 3

If we are concatenating the string for an array then you can do like this. For loop is also best solution but it becomes vast process:

if(this.questionData.length > 0) {
    this.questionData.forEach(questions => {this.questionsParams += '&question'+ questions.question +'=' + questions.value;
    });
}

Perfect solution output like this : &question1=1&question2=0&question3=1&question4=0

Answer 4

let str = '';
for (const i of [...Array(divLength).keys()]) {
  str += `Div #${i}, `;
}
console.log(str);

or a one-liner alternative,

console.log(`${[...Array(divLength).keys()].map(val => ` Div #${val}`)}`.substr(1))