Javascript 如何知道字符串以 jQuery 中的特定字符串开始/结束？
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How to know that a string starts/ends with a specific string in jQuery?
提问by Naveed
I want to know if a string starts with the specified character/string or ends with it in jQuery.
我想知道一个字符串是否以指定的字符/字符串开头或在 jQuery 中以它结尾。
For Example:
例如：
var str = 'Hello World';
if( str starts with 'Hello' ) {
alert('true');
} else {
alert('false');
}
if( str ends with 'World' ) {
alert('true');
} else {
alert('false');
}
If there is not any function then any alternative ?
如果没有任何功能，那么还有其他选择吗？
回答by Luká? Lalinsky
One option is to use regular expressions:
一种选择是使用正则表达式：
if (str.match("^Hello")) {
// do this if begins with Hello
}
if (str.match("World$")) {
// do this if ends in world
}
回答by sje397
回答by Sebastien P.
There is no need of jQuery to do that. You could code a jQuery wrapper but it would be useless so you should better use
不需要 jQuery 来做到这一点。你可以编写一个 jQuery 包装器，但它没有用，所以你应该更好地使用
var str = "Hello World";
window.alert("Starts with Hello ? " + /^Hello/i.test(str));
window.alert("Ends with Hello ? " + /Hello$/i.test(str));
as the match() method is deprecated.
因为 match() 方法已被弃用。
PS : the "i" flag in RegExp is optional and stands for case insensitive (so it will also return true for "hello", "hEllo", etc.).
PS：RegExp 中的“i”标志是可选的，代表不区分大小写（因此它也会为“hello”、“hEllo”等返回true）。
回答by Salvador Dali
You do not really need jQuery for such tasks. In the ES6 specification they already have out of the box methods startsWithand endsWith.
对于此类任务，您实际上并不需要 jQuery。在 ES6 规范中，他们已经有了开箱即用的方法startsWith和endsWith。
var str = "To be, or not to be, that is the question.";
alert(str.startsWith("To be")); // true
alert(str.startsWith("not to be")); // false
alert(str.startsWith("not to be", 10)); // true
var str = "To be, or not to be, that is the question.";
alert( str.endsWith("question.") ); // true
alert( str.endsWith("to be") ); // false
alert( str.endsWith("to be", 19) ); // true
Currently available in FF and Chrome. For old browsers you can use their polyfills or substr
目前在 FF 和 Chrome 中可用。对于旧浏览器，您可以使用它们的 polyfills 或 substr
回答by Mr. Pumpkin
You can always extend Stringprototype like this:
你总是可以String像这样扩展原型：
// Checks that string starts with the specific string
if (typeof String.prototype.startsWith != 'function') {
String.prototype.startsWith = function (str) {
return this.slice(0, str.length) == str;
};
}
// Checks that string ends with the specific string...
if (typeof String.prototype.endsWith != 'function') {
String.prototype.endsWith = function (str) {
return this.slice(-str.length) == str;
};
}
And use it like this:
并像这样使用它：
var str = 'Hello World';
if( str.startsWith('Hello') ) {
// your string starts with 'Hello'
}
if( str.endsWith('World') ) {
// your string ends with 'World'
}
回答by 16kb
ES6 now supports the startsWith()and endsWith()method for checking beginning and ending of strings. If you want to support pre-es6 engines, you might want to consider adding one of the suggested methods to the Stringprototype.
ES6 现在支持startsWith()andendsWith()方法来检查strings 的开头和结尾。如果您想支持 es6 之前的引擎，您可能需要考虑将建议的方法之一添加到String原型中。
if (typeof String.prototype.startsWith != 'function') {
String.prototype.startsWith = function (str) {
return this.match(new RegExp("^" + str));
};
}
if (typeof String.prototype.endsWith != 'function') {
String.prototype.endsWith = function (str) {
return this.match(new RegExp(str + "$"));
};
}
var str = "foobar is not barfoo";
console.log(str.startsWith("foob"); // true
console.log(str.endsWith("rfoo"); // true
