重写与underscore库启发的invoke函数时遇到问题。

huangapple
go评论105阅读模式
英文:

Having a problem with rewriting invoke function inspired by underscore library

问题

I'm a beginner and trying to rewrite an underscore function _.invoke.
I'm trying to make the function so it returns an array with the results of calling the method on each value in the collection.

  1. _.invoke = function(collection, methodName) {
  2.   var result = [];
  3.   if (Array.isArray(collection)) {
  4.     for (let i = 0; i < collection.length; i++) {
  5.       methodName.call(collection[i]);
  6.       var value = collection[i][methodName];
  7.       result.push(value);
  8.     }
  9.   }
  10.   return result;
  11. }

I think my problem lays in this line:

methodName.call(collection[i]) - would like to invoke method on an object collection[i] but I would like to pass some arguments should they be included in the unit test.

I've tried so far utilizing the test: typeof(methodName) === "function" and writing a function that would test whether the method is a function.

英文:

I'm a beginner and trying to rewrite an underscore function _.invoke.
I'm trying to make the function so it returns an array with the results of calling the method on each value in the collection.

  1. _.invoke = function(collection, methodName) {
  2.   var result = [];
  3.   if (Array.isArray(collection)) {
  4.     for (let i = 0; i < collection.length; i++) {
  5.       methodName.call(collection[i])
  6.       var value = collection[i][methodName]
  7.       result.push(value)
  8.     }
  9.   }
  10.   return result
  11. }

I think my problem lays in this line:

methodName.call(collection[i]) - would like to invoke method on an object collection[i] but I would like to pass some arguments should they be included in the unit test.

I've tried so far utilizing the test : typeof(methodName) === "function" and writing a function that would test whether the method is a function.

答案1

得分: 1

  1. _.invoke = function(collection, methodName, ...args) {
  2.   if (!Array.isArray(collection)) {
  3.      return [];
  4.   }
  5.   const out = []; 
  6.   for(const item of collection){
  7.     if(typeof item[methodName] === 'function')
  8.       out.push(item[methodName].apply(item, args));
  9.     }
  10.   }
  11.   return out;
  12. }
  14. const collection = [...];
  15. const allHaveMethod = _.invoke(collection, 'method', 'arg1', 'arg2').length === collection.length;
英文:

Here you can invoke with arguments.

  1. _.invoke = function(collection, methodName, ...args) {
  2.   if (!Array.isArray(collection)) {
  3.      return [];
  4.   }
  5.   const out = []; 
  6.   for(const item of collection){
  7.     if(typeof item[methodName] === 'function')
  8.       out.push(item[methodName].apply(item, args));
  9.     }
  10.   }
  11.   return out;
  12. }

To test that all items have a method:

  1. const collection = [...];
  2. const allHaveMethod = _.invoke(collection, 'method', 'arg1', 'arg2').length === collection.length;

答案2

得分: 1

以下是您要的翻译内容：

  1. 你的意思是这样吗？
  3. const myArr = [
  4.   { cons: function(args) { return args; } },
  5.   { cons: function(args) { return args["bla"]; } },
  6. ];
  8. const _ = {};
  9. _.invoke = (collection, methodName, ...args) => {
  10.   const result = [];
  11.   if (!Array.isArray(collection)) return result;
  13.   for (let i = 0, len = collection.length; i < len; i++) {
  14.     const item = collection[i];
  15.     const method = item[methodName];
  17.     if (typeof method === 'function') {
  18.       result.push(method.apply(item, args));
  19.     }
  20.   }
  22.   return result;
  23. };
  25. const res = _.invoke(myArr, "cons", {
  26.   "bla": "hello"
  27. });
  28. console.log(res);

这是您提供的JavaScript代码的翻译版本。

英文:

You mean something like this?

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

  1. const myArr = [
  2.   { cons:function(args) { return args } },
  3.   { cons:function(args) { return args[&quot;bla&quot;] } },
  4. ]
  6. const _ = {};
  7. _.invoke = (collection, methodName, ...args) =&gt; !Array.isArray(collection) ? [] : collection
  8. .filter(item =&gt; typeof item[methodName] === &#39;function&#39;)
  9. .map(item =&gt; item[methodName].apply(item, args));
  11. const res = _.invoke(myArr,&quot;cons&quot;,{&quot;bla&quot;:&quot;hello&quot;})
  12. console.log(res)

<!-- end snippet -->

Here is a more performant version if you need speed over a lot of entries

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

  1. const myArr = [
  2.   { cons: function(args) { return args; } },
  3.   { cons: function(args) { return args[&quot;bla&quot;]; } },
  4. ];
  6. const _ = {};
  7. _.invoke = (collection, methodName, ...args) =&gt; {
  8.   const result = [];
  9.   if (!Array.isArray(collection)) return result;
  11.   for (let i = 0, len = collection.length; i &lt; len; i++) {
  12.     const item = collection[i];
  13.     const method = item[methodName];
  15.     if (typeof method === &#39;function&#39;) {
  16.       result.push(method.apply(item, args));
  17.     }
  18.   }
  20.   return result;
  21. };
  23. const res = _.invoke(myArr, &quot;cons&quot;, {
  24.   &quot;bla&quot;: &quot;hello&quot;
  25. });
  26. console.log(res);

<!-- end snippet -->

huangapple
  • 本文由 发表于 2023年5月11日 18:24:02
  • 转载请务必保留本文链接：https://go.coder-hub.com/76226594.html
  • arrays
  • javascript
  • methods
  • object
  • underscore.js
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