# Linear search

JavaScript, Algorithm, Array · Dec 28, 2020

Finds the first index of a given element in an array using the linear search algorithm.

- Use a
`for...in`

loop to iterate over the indexes of the given array. - Check if the element in the corresponding index is equal to
`item`

. - If the element is found, return the index, using the unary
`+`

operator to convert it from a string to a number. - If the element is not found after iterating over the whole array, return
`-1`

.

```
const linearSearch = (arr, item) => {
for (const i in arr) {
if (arr[i] === item) return +i;
}
return -1;
};
```

```
linearSearch([2, 9, 9], 9); // 1
linearSearch([2, 9, 9], 7); // -1
```