JavaScript: What is the best way to increase the size of an array by adding new elements

Question

JavaScript: What is the best way to increase the size of an array by adding new elements

I am attempting to generate an array containing the first 100 prime numbers. Here is the code I have written:

var primeArray= [];
var num= primeArray.length;

function checkIfPrime(n)
{
    if(n < 2)
    {
        return false;
    }

    for(i=2; i<Math.sqrt(n); i++)
    {
        if(n%i===0)
        {
            return false;
        }
    }
    return true
};

while(num<100)
{
    var j=2
    if(checkIfPrime(j)==true)
    {
        primeArray.push(j);
    }
    j=j+1
}

As a beginner in Javascript, I have verified that the checkIfPrime function works well even with large numbers.

However, upon running the program, I encounter the following error:

FATAL ERROR: JS Allocation failed - process out of memory

I suspect there might be an issue with this part of the code:

while(num<100)
{
    var j=2
    if(checkIfPrime(j)=true)
    {
        primeArray.push(j);
    }
    j=j+1
}
console.log(primeArray)

But I cannot pinpoint the exact problem.

javascript arrays

Answer 1

Answer №1

Each time the loop runs, you are consistently assigning the value j=2, and the variable nombre remains unchanged, causing the loop to run indefinitely. Remember that in JavaScript, literal values are set by value, not reference, so simply writing nombre = premier.length will not dynamically update.

In addition, be cautious of statements like if( x = true) as this will actually assign the truthy value to x and always pass the condition automatically. If x is a function call in this context, it results in invalid syntax.

Perhaps you intended for this code instead:

var j = 2;
while(premier.length < 100) {
    if( isPrime(j)) premier.push(j);
    j++;
}

Answer 2

Each time the loop runs, you are consistently assigning the value j=2, and the variable nombre remains unchanged, causing the loop to run indefinitely. Remember that in JavaScript, literal values are set by value, not reference, so simply writing nombre = premier.length will not dynamically update.

In addition, be cautious of statements like if( x = true) as this will actually assign the truthy value to x and always pass the condition automatically. If x is a function call in this context, it results in invalid syntax.

Perhaps you intended for this code instead:

var j = 2;
while(premier.length < 100) {
    if( isPrime(j)) premier.push(j);
    j++;
}

JavaScript: What is the best way to increase the size of an array by adding new elements

Answer №1

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