pushing objects to array in for loop

Question

so i have a problem with some seemingly simple code. i am trying to calculate the points on a slope of 1/2. but all I am getting is the empty array object.

const canvas = {
  width: 1200,
  height: 600
};
const slopeValues = [];
for (let i = canvas.height / 2; i < canvas.height / 2; i--) {
  let obj = {};
  obj.x = i;
  slopeValues.push(obj);
}

console.log(slopeValues)

I should also mention that I do have the original code structured in a test suite(mocha). that shouldn't effect it but I'm not sure as I'm new to TDD.

let i = canvas.height / 2; i < canvas.height If i is initialized to be equal to canvas.height, then it will never be < than canvas.height. — CertainPerformance
– CertainPerformance, Commented May 31, 2018 at 2:21
You are initializing i in the loop as canvas.height / 2, which doesn't meet the condition i < canvas.height / 2. Nothing in the body of the for loop is executed, so slopeValues will be the empty array. — Raghav M
– Raghav M, Commented May 31, 2018 at 2:21

Eddie D · Accepted Answer · 2018-05-31 02:23:48Z

2

Your for loop condition is off. You set i = height / 2 and set the condition to i < height / 2. The condition is already false because (i == height / 2) != (i < height)

Try this one instead:

const canvas = {
  width: 1200,
  height: 600
};
const slopeValues = [];
for (let i = canvas.height / 2; i >= 0 / 2; i--) {
  let obj = {};
  obj.x = i;
  slopeValues.push(obj);
}

console.log(slopeValues)

answered May 31, 2018 at 2:23

Eddie D

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Comments

AJ Genung · Accepted Answer · 2018-05-31 02:30:38Z

0

Your initializing I to be 300, and looping through while i < 300. That evaluates to false the first time the loop tries to run so the code in the for loop is ignored.

answered May 31, 2018 at 2:30

AJ Genung

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