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React: Difference between revisions
→Functional concepts
add upto currying function |
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| Line 1,088: | Line 1,088: | ||
e.g. currying | e.g. currying | ||
< | <source lang="js"> | ||
const userLogs = userName => message => | const userLogs = userName => message => | ||
console.log(`${userName} -> ${message}`); | console.log(`${userName} -> ${message}`); | ||
| Line 1,105: | Line 1,105: | ||
// grandpa23 -> attempted to load 20 fake members | // grandpa23 -> attempted to load 20 fake members | ||
// grandpa23 -> encountered an error loading members | // grandpa23 -> encountered an error loading members | ||
</source> | |||
=== Recursion === | |||
<source lang="js"> | |||
const countdown = (value, fn) => { | |||
fn(value); | |||
return value > 0 ? countdown(value - 1, fn) : value; | |||
}; | |||
countdown(10, value => console.log(value)); | |||
// 10 | |||
// 9 | |||
// 8 | |||
// 7 | |||
// 6 | |||
// 5 | |||
// 4 | |||
// 3 | |||
// 2 | |||
// 1 | |||
// 0 | |||
</source> | |||
recursion is well-suited for searching through data structures | |||
<source lang="js"> | |||
const dan = { | |||
type: "person", | |||
data: { | |||
gender: "male", | |||
info: { | |||
id: 22, | |||
fullname: { | |||
first: "Dan", | |||
last: "Deacon" | |||
} | |||
} | |||
} | |||
}; | |||
const deepPick = (fields, object = {}) => { | |||
const [first, ...remaining] = fields.split("."); | |||
return remaining.length | |||
? deepPick(remaining.join("."), object[first]) | |||
: object[first]; | |||
}; | |||
deepPick("type", dan); // "person" | |||
deepPick("data.info.fullname.first", dan); // "Dan" | |||
deepPick("data.info.fullname.first", dan); // "Deacon" | |||
// First Iteration | |||
// first = "data" | |||
// remaining.join(".") = "info.fullname.first" | |||
// object[first] = { gender: "male", {info} } | |||
// Second Iteration | |||
// first = "info" | |||
// remaining.join(".") = "fullname.first" | |||
// object[first] = {id: 22, {fullname}} | |||
// Third Iteration | |||
// first = "fullname" | |||
// remaining.join("." = "first" | |||
// object[first] = {first: "Dan", last: "Deacon" } | |||
// Finally... | |||
// first = "first" | |||
// remaining.length = 0 | |||
// object[first] = "Deacon" | |||
</source> | </source> | ||