我如何让 JavaScript 在字符之前获取子字符串？

How do I have JavaScript get a substring before a character?

提问by johnnyjw

Let's say I have a paragraph that says 55+5. I want to have JavaScript return everything before the plus. Is this possible using substrings?

假设我有一段说 55+5。我想让 JavaScript 在加号之前返回所有内容。这可以使用子字符串吗？

回答by arjay07

Do you mean substring instead of subscript? If so. Then yes.

你的意思是子串而不是下标？如果是这样的话。好的。

var string = "55+5"; // Just a variable for your input.

function getBeforePlus(str){

    return str.substring(0, str.indexOf("+")); 
   /* This gets a substring from the beginning of the string 
      to the first index of the character "+".
   */

}

Otherwise, I recommend using the String.split()method.

否则，我建议使用String.split()方法。

You can use that like so.

你可以像这样使用它。

var string = "55+5"; // Just a variable for your input.

function getBeforePlus(str){

    return str.split("+")[0]; 
    /* This splits the string into an array using the "+" 
       character as a delimiter.
       Then it gets the first element of the split string.
    */

}

回答by qxu21

Yes. Try the String.split method: https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/String/split

是的。尝试 String.split 方法：https: //developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/String/split

split() returns an array of strings, split by the character you pass to it (in your case, the plus). Just use the first element of the array; it will have everything before the plus:

split() 返回一个字符串数组，由您传递给它的字符分割（在您的情况下，加号）。只需使用数组的第一个元素；它将拥有加号之前的所有内容：

var string = "foo-bar-baz"
var splitstring = string.split('-')
//splitstring is a 3 element array with the elements 'foo', 'bar', and 'baz'

回答by mfink

Use splitand shift.

使用split和shift。

var str = '55+5';

var beforePlus = str.split('+').shift();

console.log(beforePlus);
// -> "55"