So I have to find the largest number that contains n digits. For example, if n=2, then the largestNumber = 99. This was my answer.

function largestNumber(n) {
    var num = [];
    n = num.length;
    for(var i = 0; i < n; i++){
        num[i] = "9";
    };
    var large = +(num.join(''));
    return large;
}

Unfortunately, it returned "0". When I tried to console.log the array.

function largestNumber(n) {
    var num = [];
    n = num.length;
    for(var i = 0; i < n; i++){
        num[i] = "9";
    };
    return num;
}

console.log(largestNumber(2));

I got an empty array instead of ["9", "9"]. Why is my array not forming?

So I have to find the largest number that contains n digits. For example, if n=2, then the largestNumber = 99. This was my answer.

function largestNumber(n) {
    var num = [];
    n = num.length;
    for(var i = 0; i < n; i++){
        num[i] = "9";
    };
    var large = +(num.join(''));
    return large;
}

Unfortunately, it returned "0". When I tried to console.log the array.

function largestNumber(n) {
    var num = [];
    n = num.length;
    for(var i = 0; i < n; i++){
        num[i] = "9";
    };
    return num;
}

console.log(largestNumber(2));

I got an empty array instead of ["9", "9"]. Why is my array not forming?

• javascript

• 2 Remove n = num.length;. That line is pointless and discards the parameter you passed to the function by resetting it to 0. – Sebastian Simon Commented Oct 9, 2016 at 19:45
• 2 Simpler method: function largestNumber(n) { return Math.pow(10, n) - 1; } – Amit Commented Oct 9, 2016 at 19:51
• Of course, 99 is not the largest number that contains exactly two digits. – georg Commented Oct 9, 2016 at 20:26
• @georg What do you mean? 0xFF? 9e9? – Bergi Commented Oct 9, 2016 at 20:44
• @Bergi: yep, the assignment is pretty sloppy formulated. – georg Commented Oct 10, 2016 at 9:50

4 Answers 4

Why not use (10^n)-1 ?

Math.pow(10,n)-1

You are resetting n to 0 by assigning it with n = num.length; right after defining num as an empty array. Just drop this line and you should be fine.

Using n as the power of 10 and subtracting 1 from the result gives you the correct answer for any integer value of n.

def largestNumber(n):
    large = (10 ** n) -1
    print(large)
largestNumber(2)

I did it like this:

function largestNumber(n) {
let number = "9";
for(let i=1;i<n;i++){
    number += "9";
}
return parseInt(number);
}