reduce

问题 I am trying to aggregate the same key values into an array by value. so for example I have an array of objects, like so const data = [{foo: true},{foo: false},{bar: true},{buzz: false}] when they get aggregated the array transforms into [ foo: {true: [{foo: true}], false: [{foo: false}]}, bar: {true: [{bar: true}]}, buzz: {false: [{buzz: false}]} ] the array entries is the original object. Now I know the keys that I want to group by.. they are foo, bar, buzz and fizz. But fizz is not part of

问题 I am trying to aggregate the same key values into an array by value. so for example I have an array of objects, like so const data = [{foo: true},{foo: false},{bar: true},{buzz: false}] when they get aggregated the array transforms into [ foo: {true: [{foo: true}], false: [{foo: false}]}, bar: {true: [{bar: true}]}, buzz: {false: [{buzz: false}]} ] the array entries is the original object. Now I know the keys that I want to group by.. they are foo, bar, buzz and fizz. But fizz is not part of

问题 I am trying to aggregate the same key values into an array by value. so for example I have an array of objects, like so const data = [{foo: true},{foo: false},{bar: true},{buzz: false}] when they get aggregated the array transforms into [ foo: {true: [{foo: true}], false: [{foo: false}]}, bar: {true: [{bar: true}]}, buzz: {false: [{buzz: false}]} ] the array entries is the original object. Now I know the keys that I want to group by.. they are foo, bar, buzz and fizz. But fizz is not part of

问题 I have object: const pairs = { A: { D: [1, 2, 3] }, B: { D: [3, 2, 1] }, C: { D: [4, 3, 2, 1], B: [0, 1, 2, 3] } }; How can I get it fliped? const fliped = { D: { A: [1, 2, 3], B: [3, 2, 1], C: [4, 3, 2, 1] }, B: { C: [0, 1, 2, 3] } }; ES6 solution will be great I tried something like, but find that im not very good with reduce method and start thinkind about ugly imperative solution: Object.entries(pairs).reduce( (acc, [key1, value]) => Object.keys(value).reduce( (acc, key2) => ({ ...acc,

问题 I have object: const pairs = { A: { D: [1, 2, 3] }, B: { D: [3, 2, 1] }, C: { D: [4, 3, 2, 1], B: [0, 1, 2, 3] } }; How can I get it fliped? const fliped = { D: { A: [1, 2, 3], B: [3, 2, 1], C: [4, 3, 2, 1] }, B: { C: [0, 1, 2, 3] } }; ES6 solution will be great I tried something like, but find that im not very good with reduce method and start thinkind about ugly imperative solution: Object.entries(pairs).reduce( (acc, [key1, value]) => Object.keys(value).reduce( (acc, key2) => ({ ...acc,

问题 This question already has answers here : How to write the dataframes in a list to a single csv file (2 answers) Closed 4 years ago . I'm trying to use the Reduce function in R to use the merge function across multiple dataframes. The problem is, I would like to use the merge function with the argument all=T , and there seems to be nowhere to specify this in the higher-order Reduce function. So I'd like: a <- data.frame(id=c(1, 2, 3, 4), a=c('a', 'b', 'c', 'd')) b <- data.frame(id=c(1, 2, 5, 6

问题 This question already has answers here : How to write the dataframes in a list to a single csv file (2 answers) Closed 4 years ago . I'm trying to use the Reduce function in R to use the merge function across multiple dataframes. The problem is, I would like to use the merge function with the argument all=T , and there seems to be nowhere to specify this in the higher-order Reduce function. So I'd like: a <- data.frame(id=c(1, 2, 3, 4), a=c('a', 'b', 'c', 'd')) b <- data.frame(id=c(1, 2, 5, 6

问题 This question already has answers here : How to write the dataframes in a list to a single csv file (2 answers) Closed 4 years ago . I'm trying to use the Reduce function in R to use the merge function across multiple dataframes. The problem is, I would like to use the merge function with the argument all=T , and there seems to be nowhere to specify this in the higher-order Reduce function. So I'd like: a <- data.frame(id=c(1, 2, 3, 4), a=c('a', 'b', 'c', 'd')) b <- data.frame(id=c(1, 2, 5, 6

问题 What is the equivalent of of Scala's great foldLeft in Java 8? I was tempted to think it was reduce , but reduce has to return something of identical type to what it reduces on. Example: import java.util.List; public class Foo { // this method works pretty well public int sum(List<Integer> numbers) { return numbers.stream() .reduce(0, (acc, n) -> (acc + n)); } // this method makes the file not compile public String concatenate(List<Character> chars) { return chars.stream() .reduce(new

问题 What is the equivalent of of Scala's great foldLeft in Java 8? I was tempted to think it was reduce , but reduce has to return something of identical type to what it reduces on. Example: import java.util.List; public class Foo { // this method works pretty well public int sum(List<Integer> numbers) { return numbers.stream() .reduce(0, (acc, n) -> (acc + n)); } // this method makes the file not compile public String concatenate(List<Character> chars) { return chars.stream() .reduce(new