How do I put variables inside javascript strings?

Question

With Node.js v4 , you can use ES6's Template strings

var my_name = 'John';
var s = `hello ${my_name}, how are you doing`;
console.log(s); // prints hello John, how are you doing

You need to wrap string within backtick ` instead of '

Note, from 2015 onwards, just use backticks for templating

https://stackoverflow.com/a/37245773/294884

let a = `hello ${name}`    // NOTE!!!!!!!! ` not ' or "

Note that it is a backtick, not a quote.

---

If you want to have something similar, you could create a function:

function parse(str) {
    var args = [].slice.call(arguments, 1),
        i = 0;

    return str.replace(/%s/g, () => args[i++]);
}

Usage:

s = parse('hello %s, how are you doing', my_name);

This is only a simple example and does not take into account different kinds of data types (like %i, etc) or escaping of %s. But I hope it gives you some idea. I'm pretty sure there are also libraries out there which provide a function like this.

if you are using ES6, the you should use the Template literals.

//you can do this
let sentence = `My name is ${ user.name }. Nice to meet you.`

read more here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals

util.format does this.

It will be part of v0.5.3 and can be used like this:

var uri = util.format('http%s://%s%s', 
      (useSSL?'s':''), apiBase, path||'/');

As of node.js >4.0 it gets more compatible with ES6 standard, where string manipulation greatly improved.

The answer to the original question can be as simple as:

var s = `hello ${my_name}, how are you doing`;
// note: tilt ` instead of single quote '

Where the string can spread multiple lines, it makes templates or HTML/XML processes quite easy. More details and more capabilitie about it: Template literals are string literals at mozilla.org.

Do that:

s = 'hello ' + my_name + ', how are you doing'

Update

With ES6, you could also do this:

s = `hello ${my_name}, how are you doing`

I wrote a function which solves the problem precisely.

First argument is the string that wanted to be parameterized. You should put your variables in this string like this format "%s1, %s2, ... %s12".

Other arguments are the parameters respectively for that string.

/***
 * @example parameterizedString("my name is %s1 and surname is %s2", "John", "Doe");
 * @return "my name is John and surname is Doe"
 *
 * @firstArgument {String} like "my name is %s1 and surname is %s2"
 * @otherArguments {String | Number}
 * @returns {String}
 */
const parameterizedString = (...args) => {
  const str = args[0];
  const params = args.filter((arg, index) => index !== 0);
  if (!str) return "";
  return str.replace(/%s[0-9]+/g, matchedStr => {
    const variableIndex = matchedStr.replace("%s", "") - 1;
    return params[variableIndex];
  });
}

Examples

parameterizedString("my name is %s1 and surname is %s2", "John", "Doe");
// returns "my name is John and surname is Doe"

parameterizedString("this%s1 %s2 %s3", " method", "sooo", "goood");
// returns "this method sooo goood"

If variable position changes in that string, this function supports it too without changing the function parameters.

parameterizedString("i have %s2 %s1 and %s4 %s3.", "books", 5, "pencils", "6");
// returns "i have 5 books and 6 pencils."