To access and use a variable or function dinamically, with Name from a String in JavaScript, just use the window object, with this syntax:
window["variable_name"]

// For function
window["function_name"](parameters)
Here is some examples, see the explanations in code.
- Click on the code to select it.

1. Using variable with name stored into a string.
<script>
var vr_name = 'vr1';    // string with name of a variable

var vr1 = 'coursesweb.net/';

// uses variable with name stored as string in vr_name
// window[vr_name] /window["vr1"] is the value of vr1
var site = 'http://'+ window[vr_name];

// Test
alert(site);    // http://coursesweb.net/
</script>

2. Using variable dinamically, with name stored into a string in object.
<script>
// object with strings with variable names
var vr_name = {'v1':'vr1', 'v2':'vr2'};
var vr1 = 'coursesweb.net/';
var vr2 = 'google.com';

// uses variable dinamically, with name stored as string in vr_name
var i = 2;
var site = 'http://'+ window[vr_name['v'+ i]];

// Test
alert(site);    // http://google.com/
</script>

3. Calling function with name stored into a string.
<script>
function f1(a, b) {
  return a + b;
}

var f_name = 'f1';    // string with function name

// uses function with name stored as string in f_name
// window[f_name](parameters) calls the f1(parameters)
var sum = window[f_name](12, 23);

// Test
alert(sum);    // 35
</script>

4. Calling an object method with name stored in string into an object (use: object["method_name"](parameters)).
<script>
// object with strings with method names
var methods = {'m1':'hi1', 'm2':'hi2'};

// object with two methods
var obj = {
  'hi1': function(name) {
    return 'Hello dear '+ name;
  },
  'hi2': function(name) {
    return 'Hola '+ name;
  }
};

// uses object method with name stored as string in methods
var hi = obj[methods['m1']]('ME');

// Test
alert(hi);    // Hello dear ME
</script>

Daily Test with Code Example

HTML
CSS
JavaScript
PHP-MySQL
Which tag is used in <table> to create table header cell?
<thead> <th> <td>
<table><tr>
  <th>Title 1</th>
  <th>Title 2</th>
</tr></table>
Which CSS property sets the distance between lines?
line-height word-spacing margin
.some_class {
  line-height: 150%;
}
Which function opens a new browser window.
alert() confirm() open()
document.getElementById("id_button").onclick = function(){
  window.open("http://coursesweb.net/");
}
Indicate the PHP function that returns an array with names of the files and folders inside a directory.
mkdir() scandir() readdir()
$ar_dir = scandir("dir_name");
var_export($ar_dir);
Using Variable and Function with Name from String in JavaScript

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