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.
Image of the error
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);Best Answer
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.