Modify javascript var value without page reload

Question

I have got two php-generated values: abc and 123. This is example ready HTML document.

<script>
  var a = 'abc';
  var b = '123';
  function changeValue()
  {

  }
</script>

<button onclick="changeValue()">

<script>
  var c = 'xyz';
</script>

and I don't know how to replace value of var c when button is clicked. What function should I use in changeValue()? Please, show me right direction, then i'll find solution bedause now I have got no idea how to deal with var value.

What magic replacement are you looking for? Please elaborate — Nikhil Aggarwal
– Nikhil Aggarwal, Commented Feb 4, 2016 at 16:16
You should always put all scripts within one <script> block. — Nonemoticoner
– Nonemoticoner, Commented Feb 4, 2016 at 16:18
function changeValue() { c = "xyz"; } but define c globally i.e. without var. — Nonemoticoner
– Nonemoticoner, Commented Feb 4, 2016 at 16:19
magic is only a custom name. Point is `how to change value' after page is ready and place when i want to do change is lower than function makes chance. — Bejkrools
– Bejkrools, Commented Feb 4, 2016 at 16:20

sukalogika · Accepted Answer · 2016-02-04 16:38:37Z

1

I make a little modification of your js:

<script>
  var a = 'abc';
  var b = '123';
  function changeValue()
  {
c = 'pqr';
alert('You just set c to pqr');
  }
</script>

<button onclick="changeValue()">Change var C</button>
<button onclick="alert(c)">Check var C</button>
<script>
  var c = 'xyz';
</script>

preview: https://jsfiddle.net/sukalogika/akeqwbgy/

You can click Change var C button, and then click Check var C button

answered Feb 4, 2016 at 16:38

sukalogika

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2 Comments

Bejkrools Over a year ago

Thanks for help!! :-) In second script I use var name without var keyword too. I dont know is it matter ir isn't Now when run changing function and when I'm trying to use c then it's new value but in html core it's still old value. WIll it not distrub?

sukalogika Over a year ago

Assigning a value to an undeclared variable implicitly creates it as a global variable (it becomes a property of the global object) when the assignment is executed. developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…

Alo · Accepted Answer · 2016-02-04 16:26:33Z

1

You can change the value of variable 'c' in the do_magic_replace() function.

What you need to understand is variable scope. Any variable declared outside a function is accessible to all JavaScript code on the page; therefore, you can do the following:

function do_magic_replace() {
    c = 'Some value'; // Maybe this.value()
}

Variable scope is a fundamental concept of all programming languages. You may need to look it up with regard to JavaScript.

answered Feb 4, 2016 at 16:26

Alo

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1 Comment

Alo Over a year ago

You can refer to a previous answer for a more detailed explanation: What is the scope of variables in JavaScript?

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