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# Checking if String contains Substring

You can now use the ES6 includes() method to check if a strings contains a substring. It will determine whether that string exists in another string, returning either true or false 🤓

const word = 'sunny';

// Old way
word.indexOf('sun') !== -1; // true

// ✅ ES6 way
word.includes('sun'); // true

# Case-Sensitive

Note the comparison is case-sensitive.

'sunny'.includes('SUN'); // false

'sunny'.includes('Sun'); // false

# Array includes()

The includes() can also be applied on arrays. You can use it to check if a certain element is in an array. It will either true or false.

const weather = ['sun', 'rain', 'cloudy'];

weather.includes('sun'); // true

# Community Input

# Check if node is a descendant of a specified node

If you're checking if a node is a descendant of a specified node, you can use the contains() method. The descendant can be a child, grandchild, great-grandchild, etc.

@__offblack: When we want to check if a document element contains a particular CSS class; we would use el.classList.contains('class-name') the contains function behaves like the includes function on a DOM elements classList. Helps a long way when making decisions on toggling classes, etc through vanilla JS

const span = document.querySelector('span');
document.querySelector('div').contains(span);

# Performance Test: indexOf vs includes

Thanks Filip for creating these test cases. If you're interested in knowing the speed test for how these methods fair in different browser, check out the link.

https://jsperf.com/unggzpaz

# Resources


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