如何判断一个字符串是否包含 JavaScript 中的某个字符？
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How to tell if a string contains a certain character in JavaScript?
提问by Vivian River
I have a page with a textbox where a user is supposed to enter a 24 character (letters and numbers, case insensitive) registration code. I used maxlengthto limit the user to entering 24 characters.
我有一个带有文本框的页面，用户应该在其中输入 24 个字符（字母和数字，不区分大小写）的注册码。我曾经maxlength限制用户输入 24 个字符。
The registration codes are typically given as groups of characters separated by dashes, but I would like for the user to enter the codes without the dashes.
注册码通常以用破折号分隔的字符组的形式给出，但我希望用户输入不带破折号的代码。
How can I write my JavaScript code without jQuery to check that a given string that the user inputs does not contain dashes, or better yet, only contains alphanumeric characters?
如何在没有 jQuery 的情况下编写 JavaScript 代码来检查用户输入的给定字符串是否不包含破折号，或者更好的是，只包含字母数字字符？
回答by kemiller2002
To find "hello" in your_string
找到“你好” your_string
if (your_string.indexOf('hello') > -1)
{
alert("hello found inside your_string");
}
For the alpha numeric you can use a regular expression:
对于字母数字，您可以使用正则表达式：
http://www.regular-expressions.info/javascript.html
http://www.regular-expressions.info/javascript.html
回答by julian libor
With ES6 .includes()
使用 ES6 .includes()
"FooBar".includes("oo"); // true
"FooBar".includes("foo"); // false
"FooBar".includes("oo", 2); // false
E: Not suported by IE - instead you can use the Tilde opperator ~(Bitwise NOT) with .indexOf()
E：IE 不支持 - 相反，您可以将波浪号运算符~（按位非）与.indexOf() 一起使用
~"FooBar".indexOf("oo"); // -2 -> true
~"FooBar".indexOf("foo"); // 0 -> false
~"FooBar".indexOf("oo", 2); // 0 -> false
Used with a number, the Tilde operator effective does
~N => -(N+1). Use it with double negation !!(Logical NOT) to convert the numbers in bools:
与数字一起使用时，波浪号运算符有效
~N => -(N+1)。使用它与双重否定!!（逻辑非）来转换布尔值中的数字：
!!~"FooBar".indexOf("oo"); // true
!!~"FooBar".indexOf("foo"); // false
!!~"FooBar".indexOf("oo", 2); // false
回答by cdhowie
If you have the text in variable foo:
如果您在变量中有文本foo：
if (! /^[a-zA-Z0-9]+$/.test(foo)) {
// Validation failed
}
This will test and make sure the user has entered at least one character, and has entered onlyalphanumeric characters.
这将测试并确保用户至少输入了一个字符，并且只输入了字母数字字符。
回答by T.Todua
check if string(word/sentence...) contains specific word/character
检查 string(word/sentence...) 是否包含特定的单词/字符
if ( "write something here".indexOf("write som") > -1 ) { alert( "found it" ); }
回答by Vipin Kumar
ES6contains inbuilt method (includes) in String's prototype, which can be used to check if string contains another string or not.
ES6includes在 String's 中包含内置方法 ( ) prototype，可用于检查字符串是否包含另一个字符串。
var str = 'To be, or not to be, that is the question.';
console.log(str.includes('To be')); Following polyfill can be used to add this method in non-supported browsers. (Source)
以下 polyfill 可用于在不支持的浏览器中添加此方法。（来源）
if (!String.prototype.includes) {
String.prototype.includes = function(search, start) {
'use strict';
if (typeof start !== 'number') {
start = 0;
}
if (start + search.length > this.length) {
return false;
} else {
return this.indexOf(search, start) !== -1;
}
};
}回答by Gabriele Petrioli
Use a regular expression to accomplish this.
使用正则表达式来完成此操作。
function isAlphanumeric( str ) {
return /^[0-9a-zA-Z]+$/.test(str);
}
回答by Adam McArthur
You're all thinking too hard. Just use a simple Regular Expression, it's your best friend.
你们都想太多了。只需使用简单的正则表达式，它就是您最好的朋友。
var string1 = "Hi Stack Overflow. I like to eat pizza."
var string2 = "Damn, I fail."
var regex = /(pizza)/g // Insert whatever phrase or character you want to find
string1.test(regex); // => true
string2.test(regex); // => false
回答by Aman Maurya
var inputString = "this is home";
var findme = "home";
if ( inputString.indexOf(findme) > -1 ) {
alert( "found it" );
} else {
alert( "not found" );
}回答by Ejaz Karim
If you're searching for character(s) in the start or at the end of the string, you can also use startsWithand endsWith
如果您在字符串的开头或结尾搜索字符，您还可以使用startsWith和endsWith
const country = "pakistan";
country.startsWith('p'); // true
country.endsWith('n'); // true
回答by Mika Karjunen
Kevins answer is correct but it requires a "magic" number as follows:
凯文斯的回答是正确的，但它需要一个“魔术”数字，如下所示：
var containsChar = s.indexOf(somechar) !== -1;
In that case you need to know that -1stands for not found. I think that a bit better version would be:
在这种情况下，您需要知道-1代表not found。我认为更好的版本是：
var containsChar = s.indexOf(somechar) >= 0;
