When does a variable need to be declared outside a function in JavaScript ?

If you declare and initialized var inside a function then it will be initialized every time you call the function.

<button onclick="counterFunction()">Click me</button>

<script>

function counterFunction(){

var counter = 0;

document.getElementById("counterValue").innerHTML = counter++;

}

</script>

<p id="counterValue"></p>



Result on above example will be always 0 as the var was declared and initialized inside a function,
 every time you call the function, it gets initialized (value become 0 in this example)

Correct approach will be :


<button onclick="counterFunction()">Click me</button>

<script>

var counter = 0;

function counterFunction(){

document.getElementById("counterValue").innerHTML = counter++;

}

</script>

<p id="counterValue"></p>





            




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