How do I put variables inside javascript strings?

Question

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

That\'s how you do it in python. How can you do that in javascript/node.js?

Answer 1

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.

Answer 2

If you are using node.js, console.log() takes format string as a first parameter:

 console.log('count: %d', count);

Answer 3

Here is a Multi-line String Literal example in Node.js.

> let name = 'Fred'
> tm = `Dear ${name},
... This is to inform you, ${name}, that you are
... IN VIOLATION of Penal Code 64.302-4.
... Surrender yourself IMMEDIATELY!
... THIS MEANS YOU, ${name}!!!
...
... `
'Dear Fred,\nThis is to inform you, Fred, that you are\nIN VIOLATION of Penal Code 64.302-4.\nSurrender yourself IMMEDIATELY!\nTHIS MEANS YOU, Fred!!!\n\n'
console.log(tm)
Dear Fred,
This is to inform you, Fred, that you are
IN VIOLATION of Penal Code 64.302-4.
Surrender yourself IMMEDIATELY!
THIS MEANS YOU, Fred!!!


undefined
>

Answer 4

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 '

Answer 5

A few ways to extend String.prototype, or use ES2015 template literals.

var result = document.querySelector('#result');
// -----------------------------------------------------------------------------------
// Classic
String.prototype.format = String.prototype.format ||
  function () {
    var args = Array.prototype.slice.call(arguments);
    var replacer = function (a){return args[a.substr(1)-1];};
    return this.replace(/(\$\d+)/gm, replacer)
};
result.textContent = 
  'hello $1, $2'.format('[world]', '[how are you?]');

// ES2015#1
'use strict'
String.prototype.format2 = String.prototype.format2 ||
  function(...merge) { return this.replace(/\$\d+/g, r => merge[r.slice(1)-1]); };
result.textContent += '\nHi there $1, $2'.format2('[sir]', '[I\'m fine, thnx]');

// ES2015#2: template literal
var merge = ['[good]', '[know]'];
result.textContent += `\nOk, ${merge[0]} to ${merge[1]}`;

<pre id="result"></pre>

Answer 6

var user = "your name";
var s = 'hello ' + user + ', how are you doing';