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REACTO: Currying
Currying
a, b
curry
a
b
a b
Formal Definition:
"Currying is the process by which a function of N arguments is implemented as N single-argument functions such that first of them takes in the first argument and returns a function which takes in the 2nd argument and so on, until the Nth single-argument function finally returns the value of the multi-argument function being implemented."
Example
function addAllFour(var1, var2, var3, var4) {
return var1 + var2 - var3 * var4;
}
var curriedDoSomething = curry(addAllFour) // closure memory -> []
var firstReturn = curriedDoSomething(1) // closure memory -> [1]
var secondReturn = curriedDoSomething(2) // closure memory -> [1 , 2]
var thirdReturn = curriedDoSomething(3) // closure memory -> [1, 2, 3]
var fourthReturn = curriedDoSomething(4) // -9 (1 + 2 - 3 *4)
Example 2
function doMath(a, b, c, d) {
return a + b - c * d;
}
var curried = curry(doMath);
var makeOne = curried(1);
var makeTwo = makeOne(2);
var returned1 = makeOne(3, 4, 5); // -16 (1 + 3 - 4 * 5)
var returned2 = makeTwo(4, 5) // -17 (1 + 2 - 4 * 5)
Approach
- Function takes a function, returns a new "curried" function
- The "curry creating" function will determine the total number of N arguments required
- The "curry creating" function will keep track of the arguments as they are provided
- Once the total number of arguments provided equals the required N number of arguments, execute the original function with all the arguments
- Learn more about currying: trasb.org/currying
Possible Solution
function curry(originalFunc) {
var originalLength = originalFunc.length;
function resolver() {
var memory = Array.prototype.slice.call(arguments);
return function() {
var args = Array.prototype.slice.call(arguments);
var copy = memory.concat(args);
if (copy.length >= originalLength){
return originalFunc.apply(null, copy);
}
else return resolver.apply(null, copy);
};
};
return resolver();
}
ES6 Solution with IIFE
function curry(originalFunc) {
var originalLength = originalFunc.length;
return (function resolver() {
var memory = Array.from(arguments);
return function() {
var args = Array.from(arguments);
var copy = memory.concat(args);
if (copy.length >= originalLength){
return originalFunc(...copy);
}
else return resolver(...copy);
};
})();
}
Bonus
- The thing about the example and solution previously is that you have no control with orders. The arguments will always be passed left to right
- Edit the curry function and the example to where you control the order of the arguments
function doMath(a, b, c, d) {
return a + b - c * d;
}
var steph1 = curried(/* Do Something */ 1);
var steph2 = steph1(1, 2, 3) // 0 (1 + 2 - 3 * 1)
Possible Solution
REACTO: Currying
By pat310
REACTO: Currying
Technical interview practice problem
- 1,900