InternshipJavaScript quick reference
Everyday array, string and object methods on one page.
| Method | Purpose |
|---|---|
arr.push(x) / arr.pop() | Add to / remove from the end |
arr.map(fn) | A new array of transformed items |
arr.filter(fn) | A new array of matching items |
arr.find(fn) | The first match |
arr.includes(x) | Whether it is present |
arr.reduce(fn, start) | Combine into one value |
arr.sort((a, b) => a - b) | Sort numbers. Without this, it sorts as text |
s.trim() / s.split(",") | Tidy spaces / break into an array |
s.includes(x) / s.slice(a, b) | Search / take a part |
Object.keys(o) | The property names |
JSON.stringify / JSON.parse | To and from JSON text |
Number(x) / String(x) | Convert a value |