img.width/height inside constructor returns zero
up vote
0
down vote
favorite
I have...
var img = new Image();
img.src = 'img.png';
function Class(img){
this.img = img;
console.log(this.img.width); //0
}
var instance = new Class(img);
The console log from the code above returns 0 regardless of the image size.
If I put the console log in the update function and have it generate every frame, it does return the right value
Element.prototype.update = function(){
console.log(this.img.width); //581
}
But I don't want it to return the width every frame. I just want it once during construction. Any idea why img.width/height is always returning 0 inside the constructor?
javascript
asked Nov 8 at 4:01
snoozerviii
31
add a comment |
up vote
0
down vote
favorite
I have...
var img = new Image();
img.src = 'img.png';
function Class(img){
this.img = img;
console.log(this.img.width); //0
}
var instance = new Class(img);
The console log from the code above returns 0 regardless of the image size.
If I put the console log in the update function and have it generate every frame, it does return the right value
Element.prototype.update = function(){
console.log(this.img.width); //581
}
But I don't want it to return the width every frame. I just want it once during construction. Any idea why img.width/height is always returning 0 inside the constructor?
javascript
asked Nov 8 at 4:01
snoozerviii
31
add a comment |
up vote
0
down vote
favorite
up vote
0
down vote
favorite
I have...
var img = new Image();
img.src = 'img.png';
function Class(img){
this.img = img;
console.log(this.img.width); //0
}
var instance = new Class(img);
The console log from the code above returns 0 regardless of the image size.
If I put the console log in the update function and have it generate every frame, it does return the right value
Element.prototype.update = function(){
console.log(this.img.width); //581
}
But I don't want it to return the width every frame. I just want it once during construction. Any idea why img.width/height is always returning 0 inside the constructor?
javascript
asked Nov 8 at 4:01
snoozerviii
31
I have...
var img = new Image();
img.src = 'img.png';
function Class(img){
this.img = img;
console.log(this.img.width); //0
}
var instance = new Class(img);
The console log from the code above returns 0 regardless of the image size.
If I put the console log in the update function and have it generate every frame, it does return the right value
Element.prototype.update = function(){
console.log(this.img.width); //581
}
But I don't want it to return the width every frame. I just want it once during construction. Any idea why img.width/height is always returning 0 inside the constructor?
javascript
javascript
asked Nov 8 at 4:01
snoozerviii
31
asked Nov 8 at 4:01
snoozerviii
31
asked Nov 8 at 4:01
snoozerviii
31
asked Nov 8 at 4:01
snoozerviii
31
asked Nov 8 at 4:01
snoozerviii
31
31
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
up vote
2
down vote
accepted
Because the loading of an image resource is always asynchronous. You need to wait for its onload event:
var img = new Image();
img.src = 'https://upload.wikimedia.org/wikipedia/commons/4/47/PNG_transparency_demonstration_1.png';
function Class(img){
this.img = img;
img.onload = e => {
console.log(this.img.width);
};
}
var instance = new Class(img);answered Nov 8 at 4:06
Kaiido
37.7k45597
add a comment |
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
2
down vote
accepted
Because the loading of an image resource is always asynchronous. You need to wait for its onload event:
var img = new Image();
img.src = 'https://upload.wikimedia.org/wikipedia/commons/4/47/PNG_transparency_demonstration_1.png';
function Class(img){
this.img = img;
img.onload = e => {
console.log(this.img.width);
};
}
var instance = new Class(img);answered Nov 8 at 4:06
Kaiido
37.7k45597
add a comment |
up vote
2
down vote
accepted
Because the loading of an image resource is always asynchronous. You need to wait for its onload event:
var img = new Image();
img.src = 'https://upload.wikimedia.org/wikipedia/commons/4/47/PNG_transparency_demonstration_1.png';
function Class(img){
this.img = img;
img.onload = e => {
console.log(this.img.width);
};
}
var instance = new Class(img);answered Nov 8 at 4:06
Kaiido
37.7k45597
add a comment |
up vote
2
down vote
accepted
up vote
2
down vote
accepted
Because the loading of an image resource is always asynchronous. You need to wait for its onload event:
var img = new Image();
img.src = 'https://upload.wikimedia.org/wikipedia/commons/4/47/PNG_transparency_demonstration_1.png';
function Class(img){
this.img = img;
img.onload = e => {
console.log(this.img.width);
};
}
var instance = new Class(img);answered Nov 8 at 4:06
Kaiido
37.7k45597
Because the loading of an image resource is always asynchronous. You need to wait for its onload event:
var img = new Image();
img.src = 'https://upload.wikimedia.org/wikipedia/commons/4/47/PNG_transparency_demonstration_1.png';
function Class(img){
this.img = img;
img.onload = e => {
console.log(this.img.width);
};
}
var instance = new Class(img);var img = new Image();
img.src = 'https://upload.wikimedia.org/wikipedia/commons/4/47/PNG_transparency_demonstration_1.png';
function Class(img){
this.img = img;
img.onload = e => {
console.log(this.img.width);
};
}
var instance = new Class(img);var img = new Image();
img.src = 'https://upload.wikimedia.org/wikipedia/commons/4/47/PNG_transparency_demonstration_1.png';
function Class(img){
this.img = img;
img.onload = e => {
console.log(this.img.width);
};
}
var instance = new Class(img);answered Nov 8 at 4:06
Kaiido
37.7k45597
answered Nov 8 at 4:06
Kaiido
37.7k45597
answered Nov 8 at 4:06
Kaiido
37.7k45597
answered Nov 8 at 4:06
Kaiido
37.7k45597
37.7k45597
add a comment |
add a comment |
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