Prefer var declarations be placed at the top of their scope JS-0102
Anti-pattern
Minor
a year ago
—
a year old
All 'var' declarations must be at the top of the function scope.
14var days = 0;
15
16// Update the count down every 1 second
17var x = setInterval(function() {1819 // Get today's date and time20 now = new Date().getTime();2122 // Find the distance between now and the count down date23 distance = countDownDate - now;2425 // Time calculations for days,26 days = Math.floor(distance / (1000 * 60 * 60 * 24));272829 // Display the result in the element with id="demo"3031 document.getElementById("christmasDayCountdown").innerHTML = days + " days left until Christmas " ;3233 // If the count down is finished, write some text34 if (distance < 0) {35 clearInterval(x);36 document.getElementById("christmasDayCountdown").innerHTML = "";37 }38}, 1000);39
40// // days since christmas was OVER
41All 'var' declarations must be at the top of the function scope.
10/*Christmas day countdown */
11var countDownDate = new Date("Dec 25, 2023 23:59:59").getTime();
12var now = 0;
13var distance =0;14var days = 0;
15
16// Update the count down every 1 secondAll 'var' declarations must be at the top of the function scope.
8}
9
10/*Christmas day countdown */
11var countDownDate = new Date("Dec 25, 2023 23:59:59").getTime();12var now = 0;
13var distance =0;
14var days = 0;All 'var' declarations must be at the top of the function scope.
9
10/*Christmas day countdown */
11var countDownDate = new Date("Dec 25, 2023 23:59:59").getTime();
12var now = 0;13var distance =0;
14var days = 0;
15All 'var' declarations must be at the top of the function scope.
11var countDownDate = new Date("Dec 25, 2023 23:59:59").getTime();
12var now = 0;
13var distance =0;
14var days = 0;15
16// Update the count down every 1 second
17var x = setInterval(function() {
Description
Declare variables at the top of their scope as it improves code readability, performance and also helps in code navigation.
The vars-on-top rule generates warnings when variable declarations are not used serially at the top of a function scope or the top of a program. By default variable declarations are always moved (“hoisted”) invisibly to the top of their containing scope by the JavaScript interpreter. This rule forces the programmer to represent that behavior by manually moving the variable declaration to the top of its containing scope.
Bad Practice
// Variable declarations in a block:
function doSomething() {
var first;
if (true) {
first = true;
}
var second;
}
// Variable declaration in for initializer:
function doSomething() {
for (var i=0; i<10; i++) {}
}
Recommended
function doSomething() {
var first;
var second; //multiple declarations are allowed at the top
if (true) {
first = true;
}
}
function doSomething() {
var i;
for (i=0; i<10; i++) {}
}