Solve - regex test is not a function Error in JavaScript

Solve - regex test is not a function Error #

The "test is not a function" error occurs when the test() method is called on a value that is not a regular expression, e.g. a string. To solve the error, make sure to only call the test method on regular expressions, e.g. /[a-b]/.test('abc').

Here is an example of how the error occurs.

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const regex = '[a-z]';

// ⛔️ TypeError test is not a function
const result = regex.test('example');

We called the RegExp.test() method on a string and got the error back.

To solve this, make sure to only call the test() method on regular expressions.

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const result = /[a-z]/.test('example');

console.log(result); // 👉️ true

Notice that the regular expression is not wrapped in a string.

The forward slashes / / mark the beginning and end of the regex.

When storing the regular expression in a variable, make sure to not wrap it in quotes.

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const regex = /[a-z]/;

const result = regex.test('example');

console.log(result); // 👉️ true

If the regex is wrapped in quotes, it becomes a string and strings don't implement a test() method.