如何使后缀函数不区分大小写？

Question

I'd like to make the following code case-insensitive. If I test it out with

isSuffix("Albatross", "Ross")

it returns false, but if I try

isSuffix("Albatross", "ross")

it returns true.

How do I make it case-insensitive?

function isSuffix(str, suffix) {
  if (str.substring(str.length - suffix.length) == suffix) {
    return true;

  return false;
}

Answer 1

You can do this with regular expressions:

function isSuffix(str, suffix) {
    var regSuffix = new RegExp(suffix + '$', 'i');
    if ( regSuffix.test(str) ) {
        return true;
    }
    return false;
}

Answer 2

Just use the toLowerCase function.

function isSuffix(str, suffix) {
    str = str.toLowerCase();
    if (str.substring(str.length - suffix.length) == suffix.toLowerCase()) {
        return true;
    }
    return false;
}

Answer 3

You can use String.toLowerCase()

function isSuffix(str, suffix) {
if (str.substring(str.length - suffix.length).toLowerCase() == suffix.toLowerCase())
    return true;
return false;
}

alert(isSuffix("Albatross", "Ross"))

You could use a regular expression, too, but this is closer to your original code.

Answer 4

Change your code to this (which makes use of .toLowerCase()

function isSuffix(str, suffix) {
    return (str.substring(str.length - suffix.length).toLowerCase() == suffix.toLowerCase());
}

Answer 5

Unless you can use case insensitive regular expression match with "i" (when suffix is either just text or cost of escaping worth it) you have to convert strings to lower case first before searching. Depending on your operations per-converting one or both to lower case may give better performance if you need to perform a lot of searches.

Creating new string to simply check if suffix matches could also be wasteful. For ancient browsers you can use lastIndexOf after converting string to lower case with toLowerCase .

For more modern JavaScript code (current versions of browsers/NodeJS) use endsWith (the link also includes polyfill):

function isSuffix(str, suffix) {
   return (str.toLowerCase().endsWith(suffix.toLowerCase());
}