Currying Functions
What tasty thing is this?
The process of converting a function that accepts multiple arguments, into one that accepts a single argument, by binding some of the arguments into the original function.
function multiply(op1, op2){
return op1*op2;
}
var times5 = curry(multiply, 5);
var product = times5(4); // 20
Why Should we Curry?
To understand every function as taking
at most one argument.
To stay DRY when invoking functions that use the same arguments many times.
function tax(percent, amount){
return Math.round(amount * percent)/100;
}
var taxOf110InHawaii = tax(4.712, 110); // 5.18
var hiTax = curry(tax, 4.712);
taxOf110InHawaii = hiTax(110); // 5.18
Manually Currying
Write a function that returns another function that accesses the argument of the original function.
The original function arguments change the result of the returned function when its invoked.
function add(op1){
return function(op2){
return op1 + op2;
}
}
var add5 = add(5); // a function that adds 5
var sumOf5and4 = add5(4); // 9
var shortHand = add(5)(4); // 9
Using Curry Helper
Use a helper function to convert functions into a curried function that accepts a single argument.
function curry(fn) {
var args = Array.prototype.slice.call(arguments, 1);
return function () {
return fn.apply(this, args.concat(
Array.prototype.slice.call(arguments, 0)
));
};
}
convert a function
function concat (head, tail){
return head + tail;
}
var greet = curry(concat,'Hello ');
greet('Jason'); // Hello Jason
Using Lo-Dash Curry Helper
Use lo-dash's partial() function to convert functions into a curried function that accepts a single argument.
var _ = require('lodash');
function concat (head, tail){
return head + tail;
}
var greet = _.partial(concat,'Hello ');
greet('Jon'); // Hello Jon
Currying Functions
By Jon Borgonia
Currying Functions
basic currying in javascript
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