CODEWITHSUNDEEP
javascriptpiping
Vahid
Vahid

Reputation: 1957

How to pipe output of one method to the input of the other in Javascript?

Lets say I have an array of functions as below

var updateCountryToCanada = function (items) {
    return items.map(i => {i['country'] = 'Canada'; return i});
}

var strip_punctuation_from_name = function (items) {
    return items.map(i => {i['name'] = i['name'].replace('.', '-');
    return i}); 
}

and an array of items as below

var items = [{'name': 'John.Joo', 'height': 160, 'country':'US'},
    {'name': 'Isla', 'height': 180, 'country':'France'},
    {'name': 'Sam'}];

I put all my functions in an array

var funcs = [updateCountryToCanada, strip_punctuation_from_name]

Now, my question is how can I in JavaScript call functions one at a time and pass all items to them in a way that the result of the first function become the input to the second and so on? I want to chain them together (piping).

Upvotes: 0

Views: 351

Answers (3)

nnnnnn
nnnnnn

Reputation: 150080

You can use the .reduce() method:

var result = funcs.reduce((r, f) => f(r), items);

This calls the (r, f) => f(r) function for each item in the funcs array. The first time, r will be items. For each subsequent one r will be whatever value was returned from the previous call. f is the current item from funcs.

Expand the snippet to see the results:

var updateCountryToCanada = function (items) {
    return items.map(i => {i['country'] = 'Canada'; return i});
}

var strip_punctuation_from_name = function (items) {
    return items.map(i => {i['name'] = i['name'].replace('.', '-');
    return i}); 
}

var items = [{'name': 'John.Joo', 'height': 160, 'country':'US'},
    {'name': 'Isla', 'height': 180, 'country':'France'}];

var funcs = [updateCountryToCanada, strip_punctuation_from_name];

var result = funcs.reduce((r, f) => f(r), items);
console.log(result);

Upvotes: 4

Rounin
Rounin

Reputation: 29501

As a relatively simple approach, you can call:

functionOne();

If functionOne() looks something like:

function functionOne() {
    [... CODE ...]
    var result = [...WHATEVER...];
    functionTwo(result);
}

and functionTwo() then looks something like:

function functionTwo(input) {
    var input = input;
    [... CODE ...]
    var result = [...WHATEVER...];
    functionThree(result);
}

Then the result of functionOne() will be the input of functionTwo(), the result of functionTwo() will be the input of functionThree() etc.

Upvotes: 0

rpadovani
rpadovani

Reputation: 7360

This solution is not properly piping (as > or | in Unix), but you can do something like this:

for (i = 0; i < funcs.length; i++) {
  items = funcs[i](items);
}


var updateCountryToCanada = function (items) {
  return items.map(i => {i['country'] = 'Canada'; return i});
}

var strip_punctuation_from_name = function (items) {
  return items.map(i => {i['name'] = i['name'].replace('.', '-'); return i}); 
}


var items = [{'name': 'John.Joo', 'height': 160, 'country':'US'},
    {'name': 'Isla', 'height': 180, 'country':'France'},
    {'name': 'Sam'}];

var funcs = [updateCountryToCanada, strip_punctuation_from_name];

for (i = 0; i < funcs.length; i++) {
  items = funcs[i](items);
}

console.log(items)

Upvotes: 0

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