Baseline Widely available
The find() method of Array instances returns the first element in the provided array that satisfies the provided testing function. If no values satisfy the testing function, undefined is returned.
findIndex().indexOf(). (It's similar to findIndex(), but checks each element for equality with the value instead of using a testing function.)includes(). Again, it checks each element for equality with the value instead of using a testing function.some().filter().const array1 = [5, 12, 8, 130, 44];
const found = array1.find((element) => element > 10);
console.log(found);
// Expected output: 12
find(callbackFn)
find(callbackFn, thisArg)
callbackFn
A function to execute for each element in the array. It should return a truthy value to indicate a matching element has been found, and a falsy value otherwise. The function is called with the following arguments:
element
The current element being processed in the array.
index
The index of the current element being processed in the array.
array
The array find() was called upon.
thisArg Optional
A value to use as this when executing callbackFn. See iterative methods.
The first element in the array that satisfies the provided testing function. Otherwise, undefined is returned.
The find() method is an iterative method. It calls a provided callbackFn function once for each element in an array in ascending-index order, until callbackFn returns a truthy value. find() then returns that element and stops iterating through the array. If callbackFn never returns a truthy value, find() returns undefined. Read the iterative methods section for more information about how these methods work in general.
callbackFn is invoked for every index of the array, not just those with assigned values. Empty slots in sparse arrays behave the same as undefined.
The find() method is generic. It only expects the this value to have a length property and integer-keyed properties.
const inventory = [
{ name: "apples", quantity: 2 },
{ name: "bananas", quantity: 0 },
{ name: "cherries", quantity: 5 },
];
function isCherries(fruit) {
return fruit.name === "cherries";
}
console.log(inventory.find(isCherries));
// { name: 'cherries', quantity: 5 }
const inventory = [
{ name: "apples", quantity: 2 },
{ name: "bananas", quantity: 0 },
{ name: "cherries", quantity: 5 },
];
const result = inventory.find(({ name }) => name === "cherries");
console.log(result); // { name: 'cherries', quantity: 5 }
The following example returns the first element in the array that is a prime number, or undefined if there is no prime number.
function isPrime(n) {
if (n < 2) {
return false;
}
if (n % 2 === 0) {
return n === 2;
}
for (let factor = 3; factor * factor <= n; factor += 2) {
if (n % factor === 0) {
return false;
}
}
return true;
}
console.log([4, 6, 8, 12].find(isPrime)); // undefined, not found
console.log([4, 5, 8, 12].find(isPrime)); // 5
Note: The isPrime() implementation is for demonstration only. For a real-world application, you would want to use a heavily memoized algorithm such as the Sieve of Eratosthenes to avoid repeated calculations.
The array argument is useful if you want to access another element in the array, especially when you don't have an existing variable that refers to the array. The following example first uses filter() to extract the positive values and then uses find() to find the first element that is less than its neighbors.
const numbers = [3, -1, 1, 4, 1, 5, 9, 2, 6];
const firstTrough = numbers
.filter((num) => num > 0)
.find((num, idx, arr) => {
// Without the arr argument, there's no way to easily access the
// intermediate array without saving it to a variable.
if (idx > 0 && num >= arr[idx - 1]) return false;
if (idx < arr.length - 1 && num >= arr[idx + 1]) return false;
return true;
});
console.log(firstTrough); // 1
Empty slots in sparse arrays are visited, and are treated the same as undefined.
// Declare array with no elements at indexes 2, 3, and 4
const array = [0, 1, , , , 5, 6];
// Shows all indexes, not just those with assigned values
array.find((value, index) => {
console.log("Visited index", index, "with value", value);
return false;
});
// Visited index 0 with value 0
// Visited index 1 with value 1
// Visited index 2 with value undefined
// Visited index 3 with value undefined
// Visited index 4 with value undefined
// Visited index 5 with value 5
// Visited index 6 with value 6
// Shows all indexes, including deleted
array.find((value, index) => {
// Delete element 5 on first iteration
if (index === 0) {
console.log("Deleting array[5] with value", array[5]);
delete array[5];
}
// Element 5 is still visited even though deleted
console.log("Visited index", index, "with value", value);
return false;
});
// Deleting array[5] with value 5
// Visited index 0 with value 0
// Visited index 1 with value 1
// Visited index 2 with value undefined
// Visited index 3 with value undefined
// Visited index 4 with value undefined
// Visited index 5 with value undefined
// Visited index 6 with value 6
The find() method reads the length property of this and then accesses each property whose key is a nonnegative integer less than length.
const arrayLike = {
length: 3,
"-1": 0.1, // ignored by find() since -1 < 0
0: 2,
1: 7.3,
2: 4,
};
console.log(Array.prototype.find.call(arrayLike, (x) => !Number.isInteger(x)));
// 7.3
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