Javascript 数字比较失败 [英] Javascript number comparison fails
问题描述
我试图了解我的错误在哪里,因为 JS 不可能在数学上失败!
在 HTML 表单上,我有一个选择和 9 个文本输入.然后,在 JS 上比较输入的文本.
我的问题如下:如果我写在
new_da3 = 1400new_a3 = 1900
JS 会说 ok3.
如果我写了
new_da3 = 1900new_a3 = 1400
JS 会说不!
但是如果我写了
new_da3 = 1500new_a3 = 800
JS 会说 ok3!
为什么?1500 不是比 800 大吗?
谢谢!
HTML:
JS
函数测试(){var new_da1 = document.getElementById('new_da1').valuevar new_a1 = document.getElementById('new_a1').valuevar new_da2 = document.getElementById('new_da2').valuevar new_a2 = document.getElementById('new_a2').valuevar new_da3 = document.getElementById('new_da3').valuevar new_a3 = document.getElementById('new_a3').valuevar new_nrp = document.getElementById('new_nrp').value开关(new_nrp){案例3":if(new_a2 < new_da3 && new_da3 <= new_a3){警报('ok3')} 别的 {警报('no3')返回}情况2":if(new_a1 < new_da2 && new_da2 <= new_a2){警报('ok2')} 别的 {警报('no2')返回}情况1':if(new_da1 <= new_a1){警报('ok1')} 别的 {警报('no1')返回}休息;默认:alert("你怎么在这里?");返回;}}
因为您比较的是字符串,而不是整数.使用 parseInt
将您的值显式转换为整数.
这基本上就是你在做什么:jsFiddle 示例>
要进行转换,请将变量更改为:
var new_da1 = parseInt( document.getElementById('new_da1').value, 10);
(假设它们都是整数)
I'm trying to understand where is my error, because it's not possible that JS fails in math!
On the HTML form I have a select and 9 text input. Then, on the JS I compare the text entered.
My problem is the following: If I write on
new_da3 = 1400
new_a3 = 1900
the JS will say ok3.
If I write on
new_da3 = 1900
new_a3 = 1400
the JS will say no3!
BUT If I write on
new_da3 = 1500
new_a3 = 800
the JS WILLL SAY ok3!
Why? Isn't 1500 bigger than 800?
Thank you!
HTML:
<form>
<select id="new_nrp" onchange="selNrP(this.value);" style="background-color:#F00; color:#FFF">
<option value="" selected="selected"></option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
</select>
<?php
for($i=1; $i<=3; $i++){
print '<input type="text" size="5" maxlength="5" id="new_da'.$i.'">
<input type="text" size="5" maxlength="5" id="new_a'.$i.'">';
}
?>
<input type="submit" class="buttongreen" onClick="test()" value="Try the test function!">
</form>
JS
function test(){
var new_da1 = document.getElementById('new_da1').value
var new_a1 = document.getElementById('new_a1').value
var new_da2 = document.getElementById('new_da2').value
var new_a2 = document.getElementById('new_a2').value
var new_da3 = document.getElementById('new_da3').value
var new_a3 = document.getElementById('new_a3').value
var new_nrp = document.getElementById('new_nrp').value
switch(new_nrp){
case '3':
if(new_a2 < new_da3 && new_da3 <= new_a3){
alert('ok3')
} else {
alert('no3')
return
}
case '2':
if(new_a1 < new_da2 && new_da2 <= new_a2){
alert('ok2')
} else {
alert('no2')
return
}
case '1':
if(new_da1 <= new_a1){
alert('ok1')
} else {
alert('no1')
return
}
break;
default:
alert("Why are you here?");
return;
}
}
Because you're comparing strings, not integers. Use parseInt
to explicitly cast your values as integers.
Here's essentially what you're doing: jsFiddle example
To do the conversion, change your variables to something like:
var new_da1 = parseInt( document.getElementById('new_da1').value, 10);
(assuming they're all integers)
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