JavaScript .findIndex()

The .findIndex() array method returns the first index that passes the callback function’s test. Returns -1 if no element passes the test.

Syntax

array.findIndex((element, index, array) => {...});

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A function can be invoked with three arguments:

• element: The current element we are iterating through.
• index (optional): The index of the array element.
• array (optional): The array itself.

Examples

Find the first element that satisfies the condition:

const cats = ['Kiki', 'Leo', 'Milo', 'Cleo', 'Lily', 'Luna'];

const findLily = cats.findIndex((cat) => {
  return cat == 'Lily';
});

console.log(findLily);
// Output: 4

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If no element satisfies the condition, the result will be -1:

const cats = ['Kiki', 'Leo', 'Milo', 'Cleo', 'Luna'];

const findLily = cats.findIndex((cat) => {
  return cat == 'Lily';
});

console.log(findLily);
// Output: -1

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