Attempting to understand why the console is not logging as anticipated when calling the function with the argument

Question

Attempting to understand why the console is not logging as anticipated when calling the function with the argument

var interval = window.setInterval(animate, 500);
var i = 5;
function animate() {
    if (i > 1) {
        i--;
        console.log(i);
    } else {
        window.clearInterval(interval);
    }
}
animate();

This block of javascript code initializes the variable i with a value of 5 and logs numbers from 5 to 1. View a live demo on this fiddle link.

In an attempt to pass the initial number as an argument to the animate() function, some modifications were made:

var interval = window.setInterval(animate, 500);
var i;
function animate(i) {
    if (i > 1) {
        i--;
        console.log(i);
    } else {
        window.clearInterval(interval);
    }
}
animate(10);

Unfortunately, this revised version only displays the number 9 instead of the expected sequence from 10 to 1. Check out the demonstration at this fiddle link.

If anyone has insights on what might be causing this issue, your input would be greatly appreciated.

javascript

Answer 1

Answer №1

One option is to have the function call itself recursively and utilize setTimeout with an anonymous function that includes the current value of i.

function performAnimation(i) {
    if (i > 1) {
        i -= 1;
        console.log(i);
        setTimeout(function() {
            animate(i);
        }, 500);
    }
}

performAnimation(10);

This approach eliminates the need to manage an interval, allowing the animation to be controlled solely by the animate() method. It's a cleaner solution in my opinion.

Here is a working demonstration on jsfiddle: http://jsfiddle.net/UNkhK/

If you prefer to retain control over the timeout, you can enhance the functionality by transforming the function into an object like this:

function Animation(delay) {
    this.delay = delay || 500;
    this.timeout = null;
}

Animation.prototype.performAnimation = function(i) {
    if (i > 1) {
        i -= 1;
        console.log(i);
        var self = this;
        this.timeout = setTimeout(function() {
            self.performAnimation(i);
        }, this.delay);
    }
}

Animation.prototype.stopAnimation = function() {
    clearTimeout(this.timeout);
}

var animation = new Animation(500);
animation.performAnimation(10);

// Testing
setTimeout(function() {
    animation.stopAnimation();
    console.log('Animation stopped prematurely!');
}, 2000);

Check out the working fiddle/demo here: http://jsfiddle.net/5dZyd/

Answer 2

One option is to have the function call itself recursively and utilize setTimeout with an anonymous function that includes the current value of i.

function performAnimation(i) {
    if (i > 1) {
        i -= 1;
        console.log(i);
        setTimeout(function() {
            animate(i);
        }, 500);
    }
}

performAnimation(10);

This approach eliminates the need to manage an interval, allowing the animation to be controlled solely by the animate() method. It's a cleaner solution in my opinion.

Here is a working demonstration on jsfiddle: http://jsfiddle.net/UNkhK/

If you prefer to retain control over the timeout, you can enhance the functionality by transforming the function into an object like this:

function Animation(delay) {
    this.delay = delay || 500;
    this.timeout = null;
}

Animation.prototype.performAnimation = function(i) {
    if (i > 1) {
        i -= 1;
        console.log(i);
        var self = this;
        this.timeout = setTimeout(function() {
            self.performAnimation(i);
        }, this.delay);
    }
}

Animation.prototype.stopAnimation = function() {
    clearTimeout(this.timeout);
}

var animation = new Animation(500);
animation.performAnimation(10);

// Testing
setTimeout(function() {
    animation.stopAnimation();
    console.log('Animation stopped prematurely!');
}, 2000);

Check out the working fiddle/demo here: http://jsfiddle.net/5dZyd/

Answer 3

Answer №2

Function parameters serve as local variables that conceal global variables. Therefore, if you opt for the same identifier j for the parameter, you won't be able to access the global variable bearing that name. It is imperative to utilize distinct variables.

var global_j;
function move(local_j) {
    if (local_j !== undefined) { // Will remain undefined when invoked from setTimeout
        global_j = local_j;
    }
    if (global_j > 1) {
        global_j--;
        console.log(global_j);
    } else {
        window.clearTimeout(timer);
    }
}
move(10);

Answer 4

Function parameters serve as local variables that conceal global variables. Therefore, if you opt for the same identifier j for the parameter, you won't be able to access the global variable bearing that name. It is imperative to utilize distinct variables.

var global_j;
function move(local_j) {
    if (local_j !== undefined) { // Will remain undefined when invoked from setTimeout
        global_j = local_j;
    }
    if (global_j > 1) {
        global_j--;
        console.log(global_j);
    } else {
        window.clearTimeout(timer);
    }
}
move(10);

Answer 5

Answer №3

Instead of utilizing the variable i, a new one was created within the function definition - this means that i inside the function animate(i) generates a fresh var i specific to that function, rather than using the global version.

var i = 10;
function animate() {
    if (i > 1) {
        i--;
        console.log(i);
    }
    /*
    rest of your code here
    */
    animate();
}

For more information on JavaScript scoping, check out javascript scoping.

It's also recommended to use setTimeout instead of setInterval. Here's more info: see here.

View the example in this JSFiddle demo.

Answer 6

Instead of utilizing the variable i, a new one was created within the function definition - this means that i inside the function animate(i) generates a fresh var i specific to that function, rather than using the global version.

var i = 10;
function animate() {
    if (i > 1) {
        i--;
        console.log(i);
    }
    /*
    rest of your code here
    */
    animate();
}

For more information on JavaScript scoping, check out javascript scoping.

It's also recommended to use setTimeout instead of setInterval. Here's more info: see here.

View the example in this JSFiddle demo.

Answer 7

Answer №4

One approach you could take is to call the function from within itself and pass the variable i:

let counter;
function countdown(i) {
   if (i > 0) {
        i--;
        console.log(i);
        counter = setTimeout(function(){ countdown(i) }, 500);
    }
}
countdown(5);

FIDDLE.

Answer 8

One approach you could take is to call the function from within itself and pass the variable i:

let counter;
function countdown(i) {
   if (i > 0) {
        i--;
        console.log(i);
        counter = setTimeout(function(){ countdown(i) }, 500);
    }
}
countdown(5);

FIDDLE.

Attempting to understand why the console is not logging as anticipated when calling the function with the argument

Answer №1

Answer №2

Answer №3

Answer №4

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