How to Check If String Contains Substring

How do I check if string contains substring?

Like this:

if (str.indexOf("Yes") >= 0)

...or you can use the tilde operator:

if (~str.indexOf("Yes"))

This works because indexOf() returns -1 if the string wasn't found at all.

Note that this is case-sensitive.

If you want a case-insensitive search, you can write

if (str.toLowerCase().indexOf("yes") >= 0)

Or:

if (/yes/i.test(str))

The latter is a regular expression or regex.

Regex breakdown:

/ indicates this is a regex
yes means that the regex will find those exact characters in that exact order
/ ends the regex
i sets the regex as case-insensitive
.test(str) determines if the regular expression matches str
To sum it up, it means it will see if it can find the letters y, e, and s in that exact order, case-insensitively, in the variable str

How to check whether a string contains a substring in JavaScript?

ECMAScript 6 introduced String.prototype.includes:

const string = "foo";
const substring = "oo";

console.log(string.includes(substring)); // true

Go test string contains substring

Use the function Contains from the strings package.

import (
    "strings"
)
strings.Contains("something", "some") // true

How to check whether a string contains a substring in Kotlin?

Kotlin has stdlib package to perform certain extension function operation over the string, you can check this method it will check the substring in a string, you can ignore the case by passing true/false value. Refer this link

"AbBaCca".contains("bac", ignoreCase = true)

How to check if a string contains a substring in Bash

You can use Marcus's answer (* wildcards) outside a case statement, too, if you use double brackets:

string='My long string'
if [[ $string == *"My long"* ]]; then
  echo "It's there!"
fi

Note that spaces in the needle string need to be placed between double quotes, and the * wildcards should be outside. Also note that a simple comparison operator is used (i.e. ==), not the regex operator =~.

How to check if a string contains a substring in Rust?

Rust has no such operator. You can use the String::contains method instead:

if a.contains("bc") {
    do_something();
}

How to see if a string ONLY contains a substring in python

No regex necessary. Relying on the fact that str.count counts non-overlapping occurrences

len(target) * data.count(target) == len(data)

Simple string methods are 400-800% faster than regex here:

>>> import re
>>> target = "World"
>>> data = "World" * 3
>>> pattern = f"^({re.escape(target)})+$"
>>> %timeit len(target) * data.count(target) == len(data)
115 ns ± 0.352 ns per loop (mean ± std. dev. of 7 runs, 10,000,000 loops each)
>>> %timeit re.match(pattern, data) is not None
456 ns ± 2.88 ns per loop (mean ± std. dev. of 7 runs, 1,000,000 loops each)
>>> %timeit bool(data.replace(target, ''))  # str.replace is faster again
51.7 ns ± 0.269 ns per loop (mean ± std. dev. of 7 runs, 10,000,000 loops each)

How to check whether a string contains a substring in Ruby

You can use the include? method:

my_string = "abcdefg"
if my_string.include? "cde"
   puts "String includes 'cde'"
end