Currying is a core concept of functional programming and a useful tool for any developer's toolbelt.
Example 1:
let f = a => b => c => a+b+c; let result = f(1)(2)(3); console.log(result); // 6
Example 2:
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>JS Bin</title> <script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.18.0/ramda.min.js"></script> </head> <body> <div id="one" style=" 100px;height: 100px;border: 2px solid black">One</div> <div id="two" style=" 100px;height: 100px;border: 2px solid black">Two</div> <div id="three" style=" 100px;height: 100px;border: 2px solid black">Three</div> </body> </html>
let one = document.getElementById('one');
let tow = document.getElementById('two');
let three = document.getElementById('three');
let f = a => b => c => a.addEventListener(b, (event)=>{
event.target.style.background = c;
});
f(one)('click')('red');
Example 3:
let one = document.getElementById('one');
let tow = document.getElementById('two');
let three = document.getElementById('three');
let f = a => b => c => a.addEventListener(b, (event)=>{
event.target.style.background = c;
});
let oneClickEvent = f(one);
let twoClickEvent = f(two);
oneClickEvent('mouseover')('red');
twoClickEvent('mouseout')('blue');
Example 4: include ramda library:
let one = document.getElementById('one');
let tow = document.getElementById('two');
let three = document.getElementById('three');
let f = R.curry((a,b,c) =>{
a.addEventListener(b, (event)=>{
event.target.style.background = c;
});
});
// with placeholder from Ramda
const clickGreen = f(R.__, 'click', 'green');
clickGreen(one);
Example 5: multi placeholders:
let one = document.getElementById('one');
let tow = document.getElementById('two');
let three = document.getElementById('three');
let f = R.curry((a,b,c) =>{
a.addEventListener(b, (event)=>{
event.target.style.background = c;
});
});
// with placeholder from Ramda
const clickColor = f(R.__, 'click', R.__);
clickColor(one, 'yellow');
clickColor(two, 'grey');
clickColor(three, 'pink');
