How to check a string data type is present in array using JavaScript ?

Last Updated : 25 May, 2023

In JavaScript, an array is a collection of data that can be of the same or different type. If we have the array containing the data, our task is to identify if it is a string data type. In this article, we will learn how to use the typeof operator.

Syntax:

typeof value

Note: The typeof operator returns a string indicating the type of the operand.

Example 1:

Input:

const sample = "GeeksforGeeks";
console.log(typeof sample);

Output : string

Example 2:

Input:

const sample = 369;
console.log(typeof sample);

Output : number

Example 3:

Input:

const sample = true;
console.log(typeof sample);

Output : boolean

Approach:

Iterate over the whole array to check if each element is a string or we will do it using for loop.
We will compare the type of iterator element with the 'string' data type using the if block.
If block will execute if it encounters the string data type.
When there is no string value present, else block will get executed.

Example 1: The following code demonstrates the case where the string is present.

JavaScript

<script>
  // Declare the array
  const arr = [1,2,3,"Geeks",4];

  // initialized flag to zero
  let flag = 0;

  // iterating over whole array element one by one
  for(let i of arr){
      // checking element is of type string or not
      if(typeof i == 'string'){
          console.log("String found");
          flag = 1;
      }
  }

  // if flag remain same that means we didn't get the string.
  if(flag==0){
      console.log("String not found");
  }
</script>

Output:

String found

Example 2: The following code demonstrates the case where the string is absent.

JavaScript

<script>
   // Declare the array
    const arr = [1,2,3,4,5];

    // initialized flag to zero
    let flag = 0;

    // iterating over whole array element one by one
    for(let i of arr){
        // checking element is of type string or not
        if(typeof i == 'string'){
            console.log("String found");
            flag = 1;
        }
    }

    // if flag remain same that means we didn't get the string.
    if(flag==0){
        console.log("String not found");
    }
</script>

Output:

String not found

We can identify any data type using the typeof operator. We can use it for other data types like eg. numbers, boolean, etc.

Approach 2: Using Array.some() and instanceof:

Initialize the Array.
Use Some method on the Array which checks the instance of each element and returns true if any string is present.
Print Evaluated result.

Example: The following code demonstrates the case where the string is present.

JavaScript

// Declare the array
const arr = [1, 2, "GFG", 4, 5];

// initialized flag to true if string found
let flag = arr.some(x => x instanceof String);


// if flag remain same that means we didn't get the string.
if (flag) {
    console.log("String not found");
}
else {
    console.log("String found")
}