为什么在JavaScript中的类变量在尝试多次调用它们或将它们分配给局部变量时会消失? [英] Why do class variables in Javascript disappear when trying to call them multiple times or assigning them to local variables?
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问题描述
var width = 10;
var data = image.data;
var height = 10;
for ( var x = 0; x < width; x++ ) {
for ( var y = 0; y < height; y++ )
var index = 4 * (y * height + x); // 0
var local_variable = ArbitraryClassInstance.getBrightness(x, y); // 0
data[ index ] = ArbitraryClassInstance.getBrightness(x, y); // 0 for both index/call
data[ index + 1 ] = ArbitraryClassInstance.getBrightness(x, y); // 0 for both index/call
}
}
context.putImageData(image, 0, 0);
当我执行代码时,index和local_variable都等于零。图像是JavaScript图像对象,数据是图像数据,宽度和高度是图像的尺寸。该类返回亮度。
Both index and local_variable are equalled to zero when I execute the code. Image is a javascript image object, data is the image data, and width and height are the dimensions of the image. The class returns brightness.
推荐答案
想象出来。我没有关闭我的大括号。对所有人发出警告。
Figured it out. I didn't close my curly brackets. A warning to all.
Chrome / Firefox正常降级,不要引发错误!
Chrome/Firefox degrade gracefully and DON'T THROW AN ERROR! You will not believe how long I was chasing this bug down.
请检查您的语法 - javascript会在C中抛出错误(指针不会出现)。
Check your syntax - javascript throws errors like pointers in C (it doesn't).
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