CODEWITHSUNDEEP
javascriptjquery
Umar Farooq
Umar Farooq

Reputation: 53

Value of variable with "var" keyword changes after using the same variable in For loop

Can someone explain that why the value of i with the var keyword changes after re-declaring the same variable in a for loop?

For example the value 10 is set to variable i and after setting the condition in for loop i < 40 the value changes to i?

var i = 10;
for (var i = 0; i < 40; i++) {
  // code block
}
document.getElementById("demo").innerHTML = i;
<div id="demo"></div>

Upvotes: 0

Views: 65

Answers (2)

Pablo Fornes Gandia
Pablo Fornes Gandia

Reputation: 29

Because in the first part of your loop, you are re-declaring the same var.

To solve this, you must change the name of the first "i" var. For example "j"

And on the first part of your loop, equal "i" to "j" -> var i = j

Here is the snippet

var j = 10;
for (var i = j; i < 40; i++) {
  // code block
}
document.getElementById("demo").innerHTML = i;
<div id="demo"></div>

Upvotes: 2

Quentin
Quentin

Reputation: 944169

var statements are scoped to the function they are declared within and the for loop is in the same function as the line immediately before it. (For historical reasons, redeclaring a variable with var doesn't throw an error, it is just silently ignored (although the assignment isn't).)

Use a let statement if you want a variable scoped to the block.

Upvotes: 4

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