# 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.
