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HTML

CSS

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JavaScript

Babel includes JSX processing.

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HTML

              
                Open the console in CodePen or in your browser's Developer Tools.
              
            
!

CSS

              
                body {
  padding: 20px;
}
              
            
!

JS

              
                console.clear();

let myArray = ['one', 2, '3', 'four', 5, NaN];

// with one argument, the item to search for
console.log(myArray.includes('one'));
console.log(myArray.includes('2'));
console.log(myArray.includes(2));
console.log(myArray.includes('3'));

// with two arguments, item and position to start searching
console.log(myArray.includes('four', 4));
console.log(myArray.includes('four', 3));

// negative position starts searching at array length + position
console.log(myArray.includes('one', -2));
console.log(myArray.includes('four', -4));

// Works with looking for NaN, which is not the case when using Array.indexOf
console.log(myArray.indexOf(NaN));
console.log(myArray.includes(NaN));


              
            
!
999px

Console