In "JavaScript Operator", I noticed that the "var" keyword is not used when the += operator is used; for example:
<p id="demo"></p>
<script>
var x = 10;
x += 5;
document.getElementById("demo").innerHTML = x;
</script>
And I tested the result of adding "var" before the statement x += 5, so: var x += 5, everything else uchanged. Then, it won't display 15; in fact, it displays nothing.
However, if using x = x + 5 instead, adding or not adding "var", it always runs and displays 15.
So, my questions are:
(1) Why "var" cannot be used with += operator?
(2) Why "var" seems to be operational when used with "x = x + 5"?
"var" keyword not used with =+ operator?
in JavaScript
Posted
In "JavaScript Operator", I noticed that the "var" keyword is not used when the += operator is used; for example:
<p id="demo"></p>
<script>
var x = 10;
x += 5;
document.getElementById("demo").innerHTML = x;
</script>
And I tested the result of adding "var" before the statement x += 5, so: var x += 5, everything else uchanged. Then, it won't display 15; in fact, it displays nothing.
However, if using x = x + 5 instead, adding or not adding "var", it always runs and displays 15.
So, my questions are:
(1) Why "var" cannot be used with += operator?
(2) Why "var" seems to be operational when used with "x = x + 5"?
Thank you!