Here is a function that can be used to replace JavaScript variable name (object property, or array element) from string with its associated value defined in JavaScript, using RegExp.
// Function that replace token from string with equivalent variable value
// Receives the string-template. Returns that string with variable names replaced
function replaceStrVar(str){
 // JavaScript & jQuery Courses - https://coursesweb.net/javascript/
  str = str.replace(/%(.*?)%/gi, function(a,b) {
    // if token is an array item, else, is object property, or variable
    if(b.match(/[a-z0-9_]+\[[a-z0-9_]+\]/i)) {
      var arritm = b.match(/([a-z0-9_]+)\[([a-z0-9_]+)\]/i);      // gets an array with the matched items
      return window[arritm[1]][arritm[2]];
    }
    else {
      var voitm = b.split('.');
      return (voitm.length == 2) ? window[voitm[0]][voitm[1]] : window[voitm[0]];
    }
  });

  return str;
}
- The names for variable /array /object.property in the string must be added within %...% .

This function can be used to create a simple template-string in JavaScript.

Here's an example of replaceStrVar() function usage, using a variable, an array, and object, and a string (template) with their names that will be replaced with their values and the result is added into a HTML element.
<div id="testpl">String Template:<br/><span class="sbi">The website: &lt;b&gt;%website%&lt;/b&gt; contains: %obj.content1%, and it has around &lt;b&gt;%visits[2]%&lt;/b&gt; uniques visitors /day.</span></div>
<button onclick="testpl()">Test replaceStrVar()</button>

<script type="text/javascript"><!--
// Function that replace token from string with equivalent variable value
function replaceStrVar(str){
 // JavaScript & jQuery Courses - https://coursesweb.net/javascript/
  str = str.replace(/%(.*?)%/gi, function(a,b) {
    // if token is an array item, else, is object property, or variable
    if(b.match(/[a-z0-9_]+\[[a-z0-9_]+\]/i)) {
      var arritm = b.match(/([a-z0-9_]+)\[([a-z0-9_]+)\]/i);      // gets an array with the matched items
      return window[arritm[1]][arritm[2]];
    }
    else {
      var voitm = b.split('.');
      return (voitm.length == 2) ? window[voitm[0]][voitm[1]] : window[voitm[0]];
    }
  });

  return str;
}

  /* Test replaceStrVar() function */

var website = 'https://coursesweb.net';      // simple variable
var visits = new Array(100, 1000, 2000);        // array

// object
var obj = new Object();
 obj.content1 = 'Web Programming Courses';
 obj.content2 = 'Web Development Tutorials';

// The string (template)
var tpl = 'The website: <b>%website%</b> contains: %obj.content1%, and it has around <b>%visits[2]%</b> uniques visitors /day.';

// adds the replacement in #testpl HTML element
function testpl(){
  document.getElementById('testpl').innerHTML = replaceStrVar(tpl);
}
//-->
</script>
Results:
String Template:
The website: <b>%website%</b> contains: %obj.content1%, and it has around <b>%visits[2]%</b> uniques visitors /day.
- To see the result, click ->

Daily Test with Code Example

HTML
CSS
JavaScript
PHP-MySQL
Which HTML5 tag can be used to embed an external application (SWF, PDF) in web page?
<mark> <embed> <canvas>
<embed src="flash_game.swf" width="450" height="350" />
Which CSS pseudo-element adds a special style to the first line of a text?
:first-letter :before :first-line
#id:first-line {
  font-weight: bold;
  color: blue;
}
Click on the window object property which gets or sets the URL of current page.
window.location window.self window.status
var url = window.location;
alert(url);
Indicate the PHP function used to get the contents of a file or page and store it into a string.
fopen() file_put_contents() file_get_contents()
$homepage = file_get_contents("http://coursesweb.net/");
echo $homepage;
Replace JavaScript variable name from string with its value

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