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Functional JavaScript First StepsWhat is functional programming?Exercise: Pure FunctionsStaying out of the loop with recursionExercise: Iteration vs. RecursionFlying first class with higher-order functionsExercise: Filter, Map, ReduceGetting closureExercise: Closures & CurryingIt's functions all the way downImmutabilityExercise: Avoiding mutationRecap & takeawaysNext steps
Exercise: Function Composition
function pipeline(...functions) {
// TODO code goes here
return function(input) {
// TODO more code goes here
};
}
pluralize = singularWord => singularWord + 's'
heart = word => "I ❤️ " + word
exclaim = sentence => sentence + "!"
showSomeLove = pipeline(pluralize, heart, exclaim);
pipelineLove = showSomeLove('pipeline')
functionLove = showSomeLove('pure function')
coffeeLove = showSomeLove('coffee break')
loveSomeShow = pipeline(exclaim, heart, pluralize)
wrongOrder = loveSomeShow('pipeline')
composedPipe = pipeline(pluralize, pipeline(heart, exclaim))
compositionLove = composedPipe('composition') // should be equivalent to: showSomeLove('composition')
composedPipe2 = pipeline(pipeline(pluralize, heart), exclaim)
compositionLove2 = composedPipe2('composition') // should be equivalent to: composedPipe('composition')
// Takes a "snake_case_string" and returns a split array of the words, e.g. ["snake", "case", "string"]
function desnake(snake_case_string) {
return snake_case_string.split('_');
}
// Takes a "string" and returns a string with the first letter capitalized, e.g. "String"
function capitalizeFirstLetter(string) {
// TODO
}
// Takes an ["array", "of", "strings"] and returns a camelized ["array", "Of", "Strings"]
function camelize(stringArray) {
// TODO
}
// Use additional cells ...
// ... to define ....
// ... more functions!
// Takes a "snake_case_string" and returns a "camelCaseString"
function snakeToCamel(snake_case_string) {
// TODO
}
snakeToCamel("super_cool_variable")
snakeToCamel("very_long_variables_should_also_work")
snakeToCamel("edgecase")
// Takes a "snake_case_string" and returns a "Train-Case-String"
function snakeToTrain(snake_case_string) {
// TODO
}
// Insert additional cells with the "+" button if you need them!
md`-----
## [=> Solutions](https://observablehq.com/@anjana/solutions-function-composition)
_Just one possible way to solve this exercise, not the only way!_
`
length([1, 2, 3])
head([1, 2, 3])
tail([1, 2, 3])
multiplied = reduce((acc, val) => acc * val, 1, [1, 2, 3])
add10 = map(val => val + 10, [1, 2, 3])
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