Javascript Ruby 的 map-like 方法

Question

JavaScript 中是否有 Ruby 的类映射语法？例如在 Ruby 中我可以这样写:

res = [[1,2,3],[4,5,6],[7,8,9]]
res = res.map { |x| x[1..2] } 
# res == [[2, 3], [5, 6], [8, 9]]

在 JavaScript 中有没有像这样工作的函数？

Answer 1

您可以查看 Underscore.js Map 辅助函数(还有 MapObject 辅助函数，类似于 map，但适用于对象): http://underscorejs.org/#map

_.map([1, 2, 3], function(num){ return num * 3; });
=> [3, 6, 9]
_.map({one: 1, two: 2, three: 3}, function(num, key){ return num * 3; });
=> [3, 6, 9]
_.map([[1, 2], [3, 4]], _.first);
=> [1, 3]

否则，您可以尝试 ES6 map 对象:https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map

var kvArray = [["key1", "value1"], ["key2", "value2"]];

// Use the regular Map constructor to transform a 2D key-value Array into a map
var myMap = new Map(kvArray);

myMap.get("key1"); // returns "value1"

// Use the spread operator to transform a map into a 2D key-value Array.
alert(uneval([...myMap])); // Will show you exactly the same Array as kvArray

// Or use the spread operator on the keys or values iterator to get 
// an array of only the keys or values
alert(uneval([...myMap.keys()])); // Will show ["key1", "key2"]

如果您决定使用 ES6，您还需要一个转译器，例如 Babel。

希望对您有所帮助。