Notes on Day 7 of 30 Days of JavaScript

• notes • series • javascript • javascript30

I rarely use the following array methods in my work so it is great to refresh my memory on their capabilities.

Table of Contents

Lessons Learned

const people = [
  { name: 'Wes', year: 1988 },
  { name: 'Kait', year: 1986 },
  { name: 'Irv', year: 1970 },
  { name: 'Lux', year: 2015 }
];

Array.prototype.some()

Given a condition, it returns true if at least one element satisfies the condition; otherwise false.

// Is at least one person 19 or older?
const CURRENT_YEAR = new Date().getFullYear()
const AGE_LIMIT = 19
people.some(a => (CURRENT_YEAR - a.year) >= AGE_LIMIT)
> true

Array.prototype.every()

Given a condition, it returns true if all elements satisfy the condition; otherwise false.

// is everyone 19 or older?
people.every(a => (CURRENT_YEAR - a.year) >= AGE_LIMIT)
> true

Array.prototype.find()

Given a condition, it returns the first element that satisfies the condition; otherwise undefined.

const comments = [
  { text: 'Love this!', id: 523423, name: 'Abby Z.' },
  { text: 'Super good', id: 823423, name: 'Bart Y.' },
  { text: 'You are the best', id: 2039842, name: 'Chan X.'},
  { text: 'Ramen is my fav food ever', id: 123523, name: 'Day W.' },
  { text: 'Nice Nice Nice!', id: 542328, name: 'Chan X.' },
];

// Find the comment by the name of 'Chan X.'
comments.find(a => a.name === 'Chan X.')

> [object Object] {
  id: 2039842,
  name: "Chan X.",
  text: "You are the best"
}

The comments array has two entries by “Chan X.” but find() will only return the comment with ID of 2039842 - the first one it encounters. The rest of the elements are ignored.

Array.prototype.findIndex()

Works similar to find() but returns the zeroth array index of the element that satisfies the condition. If no element was found then -1 is returned.

// Find the comment by the name of 'Chan X.'
comments.findIndex(a => a.name === 'Chan X.')
> 2

// Find the comment by the name of 'Emma V.'
comments.findIndex(a => a.name === 'Emma V.')
> -1

References

  • “Array Cardio Day 2.” wesbos.com, uploaded by Wes Bos, 8 Dec. 2016, <javascript30.com>.

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