Print all Negative Numbers in JavaScript Array

In JavaScript, arrays are the data structures used to store the elements. In some cases, we need to extract the elements that satisfy the condition. To print all the negative numbers from the JavaScript array, we need to iterate over the array and apply the condition to filter out the negative numbers. Once the elements are extracted, we can print them in the console.

There are various approaches in JavaScript through which one can print all the negative values which are as follows:

Using for Loop

In this approach, we are using the for loop to iterate over each element of the array and check if each element is less than 0, which means a negative number. If the number is negative then we are printing it using the console.log() method.

Syntax:

for (initialization; condition; increment/decrement) {
  // code
}

Example: The below code example uses the for Loop to print all negative numbers in a JavaScript array.

// Input arr
let arr = [12, 34, 13, -1, -4, 45, -55, -66];

// For loop to print negative numbers
for (let i = 0; i < arr.length; i++) {
  if (arr[i] < 0) {
    
    // Printing output
    console.log(arr[i]);
  }
}

-1
-4
-55
-66

Using forEach method

In this approach, we are using the forEach method to iterate over each element of the array. For each negative numbers, the element is printed to the console on separate lines using the log function.

Syntax:

array.forEach(function(currentValue, index, array) {
  // code
});

Example: The below code example uses the forEach method to print all negative numbers in a JavaScript array.

// input array
let arr = [12, 34, 13, -1, -4, 45, -55, -66];

// Printing negative numbers using forEach method
arr.forEach((number) => {
  if (number < 0) {
  
    // Printing result
    console.log(number);
  }
});

-1
-4
-55
-66

Using filter method

In this approach, we are using the built-in filter method to create the new array which consists of only the negative numbers from the input array. The resulting array is printed as the output using the log() function.

Syntax:

const res = array.filter(function(currentValue, index, array) {
  // code
});

Example: The below code example uses the filter method to print all negative numbers in a JavaScript array.

// Input arr
let arr = [12, 34, 13, -1, -4, 45, -55, -66];

// Filtering and printing negative 
// numbers  using filter method
let res = arr.filter(number => number < 0);

// Printing output
console.log(res);

[ -1, -4, -55, -66 ]

Using for...of Loop

In this approach, we are using the for...of the loop to iterative over each element of the input arr and check if the number of the array is less than 0. If the number is less than 0, then it is printed in the console.

Syntax:

for (variable of iterable) {
  // code
}

Example: The below code example uses the for...of Loop to print all negative numbers in a JavaScript array.

// Input arr
let arr = [12, 34, 13, -1, -4, 45, -55, -66];

// Printing negative numbers using for...of loop
for (let number of arr) {
  if (number < 0) {
  
    // Printing output
    console.log(number);
  }
}

-1
-4
-55
-66

Using reduce Method

In this approach, we use the reduce method to iterate over the array, accumulate the negative numbers into a new array, and then print the resulting array.

Example: The below code example uses the reduce method to collect and print all negative numbers in a JavaScript array.

let arr = [12, 34, 13, -1, -4, 45, -55, -66];
let negativeNumbers = arr.reduce((accumulator, number) => {
  if (number < 0) {
    accumulator.push(number);
  }
  return accumulator;
}, []);
console.log(negativeNumbers);