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Functional JavaScript: simple function pipeline creators
let pipe = function() {
let functions = arguments,
intermediate = undefined;
return function() {
intermediate = functions[0].apply(this, arguments);
for(let i = 1; i < functions.length; i++) {
intermediate = functions[i](intermediate);
}
return intermediate;
};
};
// Example
let concat = function(a, b) {
return a + ' ' + b;
},
format = function(message) {
return message.charAt(0).toUpperCase() + message.slice(1).toLowerCase();
},
period = function(message) {
return message.charAt(message.length - 1) !== '.' ? message + '.' : message;
},
pipedFunction = pipe(concat, format, period);
let result = pipedFunction('hello world,', 'this message has been piped');
console.log(result); // "Hello world, this message has been piped."
let pipeI = function() {
let functions = arguments;
return function * pipe() {
let i = 0, intermediate = functions[i++].apply(this, arguments);
yield intermediate;
for(; i < functions.length; i++) {
intermediate = functions[i].call(this, intermediate);
yield intermediate;
}
}
};
// Example
let concat = function(a, b) {
return a + ' ' + b;
},
format = function(message) {
return message.charAt(0).toUpperCase() + message.slice(1).toLowerCase();
},
period = function(message) {
return message.charAt(message.length - 1) !== '.' ? message + '.' : message;
},
pipedFunction = pipeI(concat, format, period);
let iterator = pipedFunction('hello world,', 'this message has been piped iteratively');
console.log(iterator.next().value); // "hello world, this message has been piped iteratively"
console.log(iterator.next().value); // "Hello world, this message has been piped iteratively"
console.log(iterator.next().value); // "Hello world, this message has been piped iteratively."
let pipeP = function() {
let functions = arguments,
recursivePromise = function(value, i) {
return new Promise((resolve, reject) => {
functions[i](value)
.then(function(intermediate) {
i += 1;
if(i < functions.length) {
recursivePromise(intermediate, i).then(resolve, reject);
} else {
resolve(intermediate);
}
}, reject);
});
};
return function() {
let i = 1;
return new Promise((resolve, reject) => {
functions[0].apply(this, arguments)
.then((intermediate) => {
recursivePromise(intermediate, i).then(resolve, reject);
}, reject);
});
};
};
// Example
let concat = function(a, b) {
let v = a + ' ' + b;
return Promise.resolve(v);
},
format = function(message) {
let v = message.charAt(0).toUpperCase() + message.slice(1).toLowerCase();
return Promise.resolve(v);
},
period = function(message) {
let v = message.charAt(message.length - 1) !== '.' ? message + '.' : message;
return Promise.resolve(v);
},
pipedFunction = pipeP(concat, format, period);
pipedFunction('hello world,', 'this message has been piped using Promises')
.then((message) => console.log(message)); // "Hello world, this message has been piped using promises."
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