jQuery/Javascript 无效的左侧赋值
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jQuery/Javascript Invalid left-hand side in assignment
提问by benhowdle89
I am using this relatively simple code:
我正在使用这个相对简单的代码：
var height = help ? 'minus' : 'plus';
var prop = $('#properties');
if(height == 'minus'){
prop.height(prop.height() -= 206);
} else {
prop.height(prop.height() += 206);
}
It fails on both lines that do the adding/subtracting! Any ideas?
它在执行加法/减法的两行上都失败了！有任何想法吗？
采纳答案by jAndy
The -=operator equals operand = operand - valuewhich in your case would look like
该-=运营商平等operand = operand - value而你的情况会是什么样子
prop.height() = prop.height() - 206;
which obviously will fail. You just need the minus operator to accomplish that task.
这显然会失败。您只需要减号运算符即可完成该任务。
prop.height(prop.height() - 206);
will do it.
会做的。
回答by Yevgeny Simkin
you can't -= a method.
你不能 -= 一个方法。
either you need to prop.height(prop.height() - 206);or collect the value first and then -= it like...
要么你需要先 prop.height(prop.height() - 206);收集价值，然后 -= 它喜欢......
var h = prop.height();
h -= 206
prop.height( h);
回答by Alex K.
prop.height() -= 206attemtps to assign to the return value, which is not a variable so impossible; same as (prop.height() = prop.height() - 206)
prop.height() -= 206尝试分配给返回值，这不是一个不可能的变量；同 ( prop.height() = prop.height() - 206)
You can instead; prop.height(prop.height() - 206);
你可以改为; prop.height(prop.height() - 206);
Or (prop.height(prop.height() + (height === 'minus' ? -206 : 206));)
或 ( prop.height(prop.height() + (height === 'minus' ? -206 : 206));)
回答by Joseph
var height = help ? 'minus' : 'plus';
var prop = $('#properties');
var propHeight = prop.height();
if(height === 'minus'){
prop.height(propHeight - 206);
} else {
prop.height(propHeight + 206);
}
回答by scott.korin
You've got your answer, but I wanted to mention why bother with an if/else for adding or subtracting:
你已经得到了答案，但我想提一下为什么要费心使用 if/else 来进行加法或减法：
// subtract height if help is true, otherwise add height
var heightmodifier = help ? -1 : 1;
var prop = $('#properties');
var propHeight = prop.height();
prop.height(propHeight + (206 * heightmodifier));
