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Array.reduce() example - JavaScript
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| /* | |
| * Array.reducer() | |
| * "The reduce() method executes a reducer function (that you provide) on each | |
| * element of the array, resulting in a single output value" - MDN Docs | |
| * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reduce | |
| */ | |
| const arr = [1, 10, 4]; | |
| // get the sum of all elements in the array | |
| const sumAll = arr.reduce((acc, curr) => acc + curr); | |
| console.log(sumAll); // 15 | |
| // get the larger number in the array | |
| const getLarger = arr.reduce((acc, curr) => acc > curr ? acc : curr); | |
| console.log(getLarger); // 10 | |
| // extracting the callback reducer function | |
| const getLargerReducer = (acc, curr) => acc > curr ? acc : curr; | |
| const getLarger = arr.reduce(getLargerReducer); | |
| console.log(getLarger); // 10 | |
| // Deeper look into the reduce() method. | |
| // syntax: arr.reduce(reduceFunction) | |
| function reduceFunction(accumulator, currentValue, index, initialValue) { | |
| // - accumulator (required): The accumulator accumulates the callback's return values. It is | |
| // the accumulated value previously returned in the last invocation of the callback, or initialValue, if supplied. | |
| // - currentValue (required): The current element being processed in the array. | |
| // - index (optional): The index of the current element being processed in the array. Starts from | |
| // index 0 if an initialValue is provided. Otherwise, starts from index 1. | |
| // - initialValue (optional): The array reduce() was called upon. | |
| const value = /* do something */ | |
| return value; // `value` will be the `curr` for the next iteration | |
| } |
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