Javascript: String.match() - 在正则表达式中传递字符串变量
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Javascript: String.match() - pass string variable in regular expression
提问by Mohitt
I tried to rewrite the method (part of tutorialon w3schools).
我试图重写该方法（w3schools教程的一部分）。
The problem is to make a variable string to become part of the regular expression.
问题是让一个变量字符串成为正则表达式的一部分。
Tutorial Sample code:
教程示例代码：
function myFunction() {
var str = "The rain in SPAIN stays mainly in the plain";
var res = str.match(/ain/gi);
console.log(res)
}
I tried:
我试过：
function myFunction() {
var str = "The rain in SPAIN stays mainly in the plain";
var test = "ain";
var re = "/"+test+"/gi";
var res = str.match(re);
console.log(res);
}
The way I tried did not work.
我尝试的方法不起作用。
回答by CD..
Use the regex constructor, like:
使用正则表达式构造函数，例如：
function myFunction() {
var str = "The rain in SPAIN stays mainly in the plain",
test = "ain",
re = new RegExp(test, 'gi'),
res = str.match(re);
console.log(res);
}
回答by Avinash Raj
You need to use RegExpconstructor if you want to pass a value of variable as regex.
RegExp如果要将变量值作为正则表达式传递，则需要使用构造函数。
var test = "ain";
var re = new RegExp(test, "gi");
If your variable contains special chars, it's better to escape those.
如果您的变量包含特殊字符，最好将其转义。
var re = new RegExp(test.replace(/(\W)/g, "\"), "gi");
回答by squiroid
Yes match()not works with string literals
Yesmatch()不适用于字符串文字
You can use var re = new RegExp(test,"gi");
您可以使用 var re = new RegExp(test,"gi");
var str = "The rain in SPAIN stays mainly in the plain";
var test = "ain";
var re = new RegExp(test,"gi");
var res = str.match(re);
console.log(res);
回答by eX0du5
You could have searched for "dynamic regular expressions" and you would have found: Javascript Regexp dynamic generation from variables?or Use dynamic (variable) string as regex pattern in JavaScriptwhich both describe it very well.
您可以搜索“动态正则表达式”，然后您会发现： Javascript Regexp dynamic generation from variables? 或在 JavaScript 中使用动态（可变）字符串作为正则表达式模式，这两者都很好地描述了它。
回答by TrapII
Note that you pass a string to match. If we follow the documentation, this will do a new RegExp(test). So you should avoid /and /gistrings and add corresponding flags to the RegExp constructor: the default constructor doesn't add neither global search (g) nor case insensitive search (i).
请注意，您将字符串传递给match. 如果我们遵循文档，这将执行new RegExp(test). 所以你应该避免/和/gi字符串，并在 RegExp 构造函数中添加相应的标志：默认构造函数既不添加全局搜索 ( g) 也不添加不区分大小写的搜索 ( i)。
So the solution to your problem:
所以你的问题的解决方案：
var str = "The rain in SPAIN stays mainly in the plain";
var test = "ain";
var res = str.match(new RegExp(test, "gi"));
This will returns :
这将返回：
Array [ "ain", "AIN", "ain", "ain" ]
Note :
笔记 ：
The form str.match(test, "gi");works only in Firefox browser but is deprecated and throws a console warning from Firefox 39 (see RGraham comment).
该表单str.match(test, "gi");仅适用于 Firefox 浏览器，但已被弃用并从 Firefox 39 中引发控制台警告（请参阅 RGraham 评论）。
