The avatar for @jerryjappinen
Jerry Jäppinen
Design, tech, engineering and science. Head of Design and User Research.
Public
New Programmer’s Handbook
Edited
Oct 14, 2024
Fork of Chapter 2: Simple programs
Importers
2 stars
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username = _.kebabCase(first_name + last_name)
.toLowerCase()
.replaceAll("-", "")
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username_is_too_long = username.length > 16
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username_is_too_long
? "Username " + username + " is too long. Please use something shorter."
: "Username is ok."
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Inputs.button("Save username", {
disabled: username_is_too_long
})
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mutable alert_message = ""
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addEventListener("offline", () => {
mutable alert_message = "🚨 Connection lost";
})
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function count_files (folder) {
return folder.length
}
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count_files(["file-1", "file-2", "file-3"])
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count_files([
"file-1",

// Subfolder
[
"file-2",
"file-3",

// Subfolder of subfolder
["file-4", "file-5", "file-6"]
]
])
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function count_all_files(filesAndSubfolders) {
var file_count = 0

for (const item of filesAndSubfolders) {

// File
if (!_.isArray(item)) {
file_count += 1

// Folder
} else {
file_count += count_all_files(item)
}

}

return file_count
}
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count_all_files(main_folder)
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main_folder = {
var simple_folder = ["file", "file", "file"]

var folder_with_subfolders = [
simple_folder,
"file"
]

var folder_with_nested_subfolders = [
simple_folder,
folder_with_subfolders,
"file"
]

return [
simple_folder,
folder_with_subfolders,
folder_with_nested_subfolders,
"file"
]
}
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function times_two (number) {
return number * 2
}
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times_two(2)
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times_two(-4)
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times_two(100 * (9 + 1))
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times_two()
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times_two("Hello world")
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times_two([1, 2, 3])
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times_two(true)
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new Error("Tried to do math with non-numbers. This is not allowed.")
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function times_two_strict(number) {
if (!_.isNumber(number)) {
throw new Error("Cannot multiply non-numbers")
}

return number * 2
}
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times_two_strict(2)
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times_two_strict("Hello world")
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sum = (a, b) => {
// Something might be wrong here...
return a - b
}
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sum_tests = [
sum(0, 0) === 0,
sum(1, 2) === 3,
sum(1, 2) === sum(2, 1),
sum(0, 10) === 10
]
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function measure_time (code) {
const start = Date.now()
code()
const end = Date.now()
return end - start
}
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count_to_billion = function () {
let x = 0
for (let i = 0; i < 1000 * 1000 * 1000; ++i) {
x++
}
return x
}
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count_duration = measure_time(count_to_billion)
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1 * 2 * 3 * 4
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5 * 6 * 7 * 8
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multiply_consecutive_numbers_1 = () => {
let i = 1
let r = ""

while (i < 8000000) {
const s = i * (i + 1) * (i + 2) * (i + 3)
r += " " + s
i += 4
}

return r.trim()
}
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multiply_consecutive_numbers_2 = () => {
let i = 1
let r = []

while (i < 8000000) {
const s = i * (i + 1) * (i + 2) * (i + 3)
r.push(s)
i += 4
}

return r.join(" ")
}
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measure_time(multiply_consecutive_numbers_1)
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measure_time(multiply_consecutive_numbers_2)
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