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| // Challenge One | |
| const arr = [{ a: 3 }, { a: 55 }, { a: 9 }, { a: 1 }]; | |
| const max = (array, arg) => { | |
| return array.reduce((a, b) => { | |
| if(typeof arg === 'string') { | |
| return a[arg] > b[arg] ? a : b; | |
| } | |
| else if(typeof arg === 'function') { | |
| return arg(a) > arg(b) ? a : b; | |
| } | |
| }) | |
| } | |
| console.log(max(arr, 'a')); //should output { a: 55 } | |
| console.log(max(arr, (x)=> { return x.a % 9 })); //should output { a : 3 } | |
| //----------------------------------------------- | |
| // Challenge Two | |
| const pipeline = (array) => { | |
| // const fnA = array[0](1, 2, 3); | |
| // const fnB = array[1](fnA); | |
| // const fnC = array[2](fnB); | |
| // return fnC | |
| return function(...args){ | |
| const fnA = array[0](...args); | |
| const fnB = array[1](fnA); | |
| const fnC = array[2](fnB); | |
| return fnC | |
| } | |
| // //BETTER SOLUTION: | |
| // return function() { | |
| // const fnA = array[0](...arguments); | |
| // const nextArray = array.slice(1); | |
| // return nextArray.reduce((prev, next) => { | |
| // return next(prev) | |
| // }, fnA) | |
| // } | |
| } | |
| const a = pipeline([ | |
| (a, b, c)=> a + b + c, | |
| (x)=> x + 1, | |
| (x)=> x - 10 | |
| ]); | |
| const b = pipeline([ | |
| (a, b, c, d)=> a * b + c * d, | |
| (x)=> x + 1, | |
| (x)=> x - 10 | |
| ]); | |
| console.log(a(1, 2, 3));//outputs -3 | |
| console.log(b(2, 3, 4, 5));//outputs 17 | |
| //----------------------------------------------- | |
| // Challenge Three | |
| const toMap = (arr, query, err) => { | |
| return arr.reduce((returnObj, item) => { | |
| let key; | |
| typeof query === 'string' ? key = item[query] : key = query(item); | |
| if(returnObj[key]) throw new Error("exception") | |
| returnObj[key] = item; | |
| return returnObj | |
| }, {}) | |
| } | |
| console.log(toMap([ | |
| { x: 3 }, | |
| { x: 6 }, | |
| { x: 8 } | |
| ], 'x')); | |
| /* | |
| { | |
| 3: { | |
| x: 3 | |
| }, | |
| 6: { | |
| x: 6 | |
| }, | |
| 8: { | |
| x: 8 | |
| } | |
| } | |
| */ | |
| console.log(toMap([ | |
| { x: 3 }, | |
| { x: 3 }, | |
| { x: 8 } | |
| ], 'x')); | |
| // //should throw an exception | |
| console.log(toMap([ | |
| { x: 3 }, | |
| { x: 6 }, | |
| { x: 8 } | |
| ], (item) => item.x * 2)); | |
| // /* | |
| // { | |
| // 12: { | |
| // x: 6 | |
| // }, | |
| // 16: { | |
| // x: 8 | |
| // }, | |
| // 6:{ | |
| // x: 3 | |
| // } | |
| // }*/ | |
| console.log(toMap([ | |
| { x: 3 }, | |
| { x: 6 }, | |
| { x: 8 } | |
| ], (item) => item.x % 2)); | |
| // //show throw exception | |
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