[英]Javascript how to compare two strings
This is the Javascript Function. 这是Javascript函数。 Please Explain How to compare two string in Javascript.
请说明如何比较Javascript中的两个字符串。
<head>
<script type="text/javascript">
/*javascript function*/
function ajax(str)
{
if (str.length==0)
{
document.getElementById("res").innerHTML="";
return;
}
if(str=="Select City")
{
alert("Please Select a City");
}
document.getElementById("res").innerHTML=="";
var url="code1.php?q="+str+"&r"+Math.random();
var obj;
try{
obj=new ActiveXObject(Microsoft.XMLHTTP);
}
catch(e)
{
try
{
obj=new XMLHttpRequest();
}
catch(e)
{
alert("Your browser not suport ajax");
}
}
obj.open('Get',url,true);
obj.send(null);
obj.onreadystatechange=function()
{
if(obj.readyState==4)
{
document.getElementById("res").innerHTML=obj.responseText;
}
}
}
</script>
</head>
<body>
<select onchange="ajax(this.value)" name="sel" id="btn"><option>Dharmashala</option><option>Manali</option><option>Shimla</option></select>
<div id="res"></div>
</body>
</html>
But it does not work please suggest me a proper method to do this. 但这是行不通的,请向我建议一种执行此操作的正确方法。
===
for string comparison ===
用于字符串比较
if(str === "Select City") {
alert("Please Select a City");`
}
How to compare strings in JavaScript? 如何比较JavaScript中的字符串? Use the
==
operator for equivalence and >
/ <
for alphabetical difference. 使用
==
运算符表示等价,并使用>
/ <
表示字母差异。
In your code, this line seems to be a bit useless: 在您的代码中,这一行似乎没有用:
document.getElementById("res").innerHTML=="";
Don't you want an assignment here ( =
)? 您不想在这里分配作业(
=
)吗?
I'm pretty sure it's not working because you have your this
context incorrect. 我敢肯定,它不工作,因为你有你的
this
方面不正确。 this.value
is trying to call the value
of your select
element instead of the selected option
. this.value
试图调用select
元素的value
而不是selected option
。 Try this: 尝试这个:
window.addEventListener('load', function(){
var select = document.getElementById('btn');
var selected = select.options[select.selectedIndex].value;
}, false);
window.addEventListener('change', function(selected) { changeHandler(selected); }, false);
function changeHandler(selected) {
// run your ajax() function
}
Also, be sure to put a value
on each of your option
elements. 另外,请确保在每个
option
元素上都赋一个value
。
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