The code consists of making an array from a range of numbers and as well having a third argument in which it indicates the steps from the numbers, if it has a step of 2 well for example it goes from [1,3,5] the code works fine except when I pass step with a negative number as an argument e.g. NumberRange(10,5,-2); That's when the error appears, in the code it shows the logic I used for a negative step.
function NumberRange(start, end, step){ var numberList = []; if(typeof(step) == 'undefined'){ if(start < end){ for(;start <= end; start++){ numberList.push(start); } console.log(numberList); } else if(start > end){ for(;start >= end;){ numberList.push(start); start -= 1; } console.log(numberList); } } else if(start > end && (Math.sign(step) == -1)){ // This is the logic I created when a negative step is given as an argument. for(;start >= end; start - step){ numberList.push(start); } console.log(numberList); } else if(start < end && (Math.sign(step) == -1)){ console.log("Negative step cant work since the value of the beginning of the list is less than the end of it") } else{ for(;start <= end;){ numberList.push(start); start += step; } console.log(numberList); } //return numberList; }; NumberRange(10,5,-2); 2 Answers
for(;condition;) is just an ugly way of writing while(condition), don't do it.
Why it doesn't work is the for(;start >= end; start - step) part, which doesn't update start, just subtracts step from it and throws the result away. Why it wouldn't work with - is that step is negative in that branch, so it should be start += step in order to count downwards.
Generally you don't need the 4 branches, instead you could set step to +/-1 if it's undefined, and if you really wanted to, you could still validate the sign of step after setting it but before using it:
function NumberRange(start, end, step) { if (typeof(step) == 'undefined') { step = Math.sign(end - start); } if (Math.sign(step) != Math.sign(end - start)) { console.log(`Can't count from ${start} to ${end} using ${step} as stepsize.`); } else { var numberList = []; if (start > end) { while (start > end) { numberList.push(start); start += step; } } else { while (start < end) { numberList.push(start); start += step; } } console.log(numberList.join()); return numberList; } } NumberRange(10, 5, -2); NumberRange(1, 2); NumberRange(2, 1); NumberRange(1, 3, 2); NumberRange(1, 3, -2); NumberRange(3, 1, -2); NumberRange(3, 1, 2);Then someone may get annoyed with having two loops with identical bodies, and after all, with a bit more complicated condition they can be collapsed into one:
function NumberRange(start, end, step) { if (typeof(step) == 'undefined') { step = Math.sign(end - start); } if (Math.sign(step) != Math.sign(end - start)) { console.log(`Can't count from ${start} to ${end} using ${step} as stepsize.`); } else { var numberList = []; while ((step > 0 && start < end) || (step < 0 && start > end)) { numberList.push(start); start += step; } console.log(numberList.join()); return numberList; } } NumberRange(10, 5, -2); NumberRange(1, 2); NumberRange(2, 1); NumberRange(1, 3, 2); NumberRange(1, 3, -2); NumberRange(3, 1, -2); NumberRange(3, 1, 2);You have a typo in the third for statement, the last part should be a subtraction assignment:
for(;start >= end; start += step){ numberList.push(start); } But the issue you are observing hints at an internal error in the V8 engine (a bug), probably an attempt to allocate a wrong amount of memory. I could reproduce it in Node.js and in Chrome with a simple endless loop like below.
var numberList = []; while (true) { numberList.push(1); }On my machine, this crashes after just a few seconds, when the array contains 112813858 elements.
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