{"componentChunkName":"component---src-templates-post-template-js","path":"/posts/en/2016-07-02-partial-application/","webpackCompilationHash":"a3ac22c47fe06e2afd02","result":{"data":{"markdownRemark":{"id":"42d30f36-6284-59e4-8b9c-2ab7efac058d","html":"

Problem

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You want to create a generic function, that produces for a given function the partial applied function.

\n

Ingredients

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Directions

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    \n
  1. \n

    Define a function that accepts another function (the one that should be partial applicable).

    \n
    function partial(fn /*, args...*/) {\n  ...\n}
    \n
    2. \n
\n\n
    \n
  1. \n

    Let the function return another function (this will be the partial applicable function).

    \n
    function partial(fn /*, args...*/) {\n  ...\n  return function() {\n    ...\n  }\n}
    \n
    2. \n
  2. \n

    Convert all but the first argument to an array by borrowing the slice() method.

    \n
    function partial(fn /*, args...*/) {\n  var args = Array.prototype.slice.call(arguments, 1);\n  return function() {\n    ...\n  };\n}
    \n
    3. \n
  3. \n

    Convert the arguments of the inner function to an array.

    \n
    function partial(fn /*, args...*/) {\n  var args = Array.prototype.slice.call(arguments, 1);\n  return function() {\n    var argsInner = Array.prototype.slice.call(arguments, 0);\n    ...\n  };\n}
    \n
    4. \n
  4. \n

    Combine the arguments of the outer function with the arguments of the inner function.

    \n
    function partial(fn /*, args...*/) {\n  var args = Array.prototype.slice.call(arguments, 1);\n  return function() {\n    var argsInner = Array.prototype.slice.call(arguments, 0);\n    var argsAll = args.concat(argsInner);\n    ...\n  };\n}
    \n
    5. \n
  5. \n

    Call the passed function using the apply() method, passing the combined arguments.

    \n
    function partial(fn /*, args...*/) {\n  var args = Array.prototype.slice.call(arguments, 1);\n  return function() {\n    var argsInner = Array.prototype.slice.call(arguments, 0);\n    var argsAll = args.concat(argsInner);\n    return fn.apply(this, argsAll);\n  };\n}
    \n
    6. \n
  6. \n

    Optional: combine the previous three steps.

    \n
    function partial(fn /*, args...*/) {\n  var args = Array.prototype.slice.call(arguments, 1);\n  return function() {\n    return fn.apply(this, args.concat(Array.prototype.slice.call(arguments, 0)));\n  };\n}
    \n
    7. \n
  7. \n

    Voilá, a perfect, tasteful generic function that creates partial applicable functions.

    \n
    function partial(fn /*, args...*/) {\n  var args = Array.prototype.slice.call(arguments, 1);\n  return function() {\n    return fn.apply(this, args.concat(Array.prototype.slice.call(arguments, 0)));\n  };\n}\nfunction createPerson(firstName, lastName) {\n  return {\n   firstName: firstName,\n   lastName: lastName\n  }\n}\nvar createPersonWithFirstNameJohn = partial(createPerson, 'John');\nvar johnDoe = createPersonWithFirstNameJohn('Doe');\nconsole.log(johnDoe.firstName);  // \"John\"\nconsole.log(johnDoe.lastName);   // \"Doe\"
    \n
    8. \n
\n

Alternative recipes

\n","fields":{"slug":"/posts/en/2016-07-02-partial-application/","tagSlugs":["/tag/java-script/"]},"frontmatter":{"date":"2016-07-02T07:00:00.000Z","description":null,"tags":["JavaScript"],"title":"Create a generic function for partial application"}}},"pageContext":{"isCreatedByStatefulCreatePages":false,"slug":"/posts/en/2016-07-02-partial-application/"}}}