Category: coding

I have the following and need to test if a user id is present anywhere in the collection.

const meetingCollection = [
  { id: "2", userIds: [12, 34, 55, 6, 7, 43543, 45345, 545] },
  { id: "21", userIds: [3, 425, 5, 33, 7, 68, 76, 99, 66, 99] },
  { id: "22", userIds: [767, 5654756, 5658, 86, 45, 23456, 666] },
  { id: "23", userIds: [6, 43562, 5645747, 4654, 2577, 4345, 45777] },
  { id: "24", userIds: [45645, 124, 4, 435, 6, 7755, 7, 8] },
  { id: "25", userIds: [1, 2, 455, 647, 753] },
]

const queryString = 7755;

meetingCollection.some(m => m.userIds.some(userId => userId === queryString))

Array.prototype.some() tests the method against each “row” of the collection and returns true on the first hit and then stops. If you have a 1000 elements and the method returns true on the 10th iteration .some() stops looping over the collection and returns true.

If a method fails to return true then false is returned.

The above example I’ve nested .some()

Try this in the console….

const meetingCollection = [
  { id: "2", userIds: [12, 34, 55, 6, 7, 43543, 45345, 545] },
  { id: "21", userIds: [3, 425, 5, 33, 7, 68, 76, 99, 66, 99] },
  { id: "22", userIds: [767, 5654756, 5658, 86, 45, 23456, 666] },
  { id: "23", userIds: [6, 43562, 5645747, 4654, 2577, 4345, 45777] },
  { id: "24", userIds: [45645, 124, 4, 435, 6, 7755, 7, 8] },
  { id: "25", userIds: [1, 2, 455, 647, 753] },
]

const findId = (queryString) => {
  return meetingCollection.some(m => m.userIds.some(userId => userId === queryString))
}

console.log(findId(2577)); // true
console.log(findId(257)); // false

I have a requirement to be able to round numbers to either a whole number or to a specified number of decimal places….

Every now and then i find myself looking over my current solution to a problem when applying it in a new project. In this case it was very simple statistics and mean values.

For example:

const dec = [2, 678, 65.67467, 10.5452453453, 1, 0];
// Required outcome to 3 decimal places
// 2, 678, 65.675, 10.545, 1, 0

// Or to 2 decimal places
// 2, 678, 65.67, 10.55, 1, 0

My solution:

const round = (n, decimal = 2) => {
    return Math.round(n * Math.pow(10, decimal)) / Math.pow(10, decimal);
};

// Quick test
dec.forEach(n => {
console.log(round(n, 3));
});

dec.forEach(n => {
console.log(round(n));
});

As an aside: I need to have a set of numbers rounded and set with 2 fixed decimal places. So the same data set would be:

const dec = [2, 678, 65.67467, 10.5452453453, 1, 0];

// Required response would be
// 2.00, 678.00, 65.67, 10.55, 1.00, 0.00

There is the Number.toFixed() method

dec.forEach(n => console.log(n.toFixed(2)));