How do I check if string contains substring? [duplicate]

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 strTo 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

You could use search or match for this.

str.search( 'Yes' )

will return the position of the match, or -1 if it isn't found.

It's pretty late to write this answer, but I thought of including it anyhow. String.prototype now has a method includes which can check for substring. This method is case sensitive.

var str = 'It was a good date';console.log(str.includes('good')); // shows trueconsole.log(str.includes('Good')); // shows false

To check for a substring, the following approach can be taken:

if (mainString.toLowerCase().includes(substringToCheck.toLowerCase())) {    // mainString contains substringToCheck}

Check out the documentation to know more.