Returning the expanded form of a number in JavaScript

The expanded form of a number breaks down each digit into its place value. For example, 1234 becomes "1000 + 200 + 30 + 4". This is useful for teaching place value concepts and number decomposition.

Problem

We need to write a JavaScript function that takes a number and returns a string showing the expanded form, indicating the place value of each non-zero digit.

Example

const num = 56577;

const expandedForm = (num = 0) => {
    const str = String(num);
    let res = '';
    let multiplier = Math.pow(10, str.length - 1);
    
    for(let i = 0; i 

50000 + 6000 + 500 + 70 + 7
10000 + 2000 + 40 + 5
7


How It Works

The function converts the number to a string to access individual digits. It calculates a multiplier starting from the highest place value (10^(length-1)). For each digit, if it's non-zero, it multiplies by the current place value and adds to the result. The multiplier decreases by 10 each iteration.

Alternative Approach Using Filter

const expandedFormFilter = (num) => {
    return String(num)
        .split('')
        .map((digit, index, arr) => {
            const placeValue = Math.pow(10, arr.length - 1 - index);
            return +digit * placeValue;
        })
        .filter(value => value > 0)
        .join(' + ');
};

console.log(expandedFormFilter(56577));
console.log(expandedFormFilter(12045));


50000 + 6000 + 500 + 70 + 7
10000 + 2000 + 40 + 5


Key Points

• Convert number to string to access individual digits
• Calculate place values using powers of 10
• Skip zero digits to avoid "0" terms in the output
• Join non-zero terms with " + " separator

Conclusion

Both approaches effectively break down numbers into their place value components. The first method uses a loop with manual string building, while the second leverages array methods for a more functional approach.