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

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.

<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.

<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.

// 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")
}

Output:

String found

Time complexity: O(N), Where N is the length of the Array. 

Auxiliary complexity: O(1), Because no extra space is used. 

abhishekaslk

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Article Tags :

• JavaScript
• Web Technologies
• JavaScript-Questions