Forward Euler in JavaScript #418
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| Original file line number | Diff line number | Diff line change |
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| function forwardEuler(time_step, n) { | ||
| const arr = [1]; | ||
| for (let i = 1; i <= n; i++) { | ||
| arr[i] = arr[i - 1] - 3 * arr[i - 1] * time_step; | ||
| } | ||
| return arr; | ||
| } | ||
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| function checkEuler(arr, time_step, threshold) { | ||
| const is_approx = true; | ||
| arr.forEach(function callback(value, i) { | ||
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There was a problem hiding this comment. I'll go from the point where this thread ended.
The arrow ( This is how an arrow function with a full function body would look: const func1 = (param1, param2) => {
// Function body goes here
};If a function only has one line in it, which is a return statement, you can omit the const func1 = (param1, param2) => {
return param1 + param2;
};
const func2 = (param1, param2) => param1 + param2;I know what you're thinking. This looks kind of weird and unreadable. But trust me, it's just a syntax that you're not used to and once you're used to seeing it, it will look completely normal and you'll be able to quickly understand its meaning. If an arrow function has only one parameter, you can also omit the const double1 = (num) => num * 2;
const double2 = num => num * 2;To give you a practical example of why you would use these forms of arrow functions, here is a snippet of code that takes an array with numbers and creates a second array where all the numbers are doubled: const doubleArr = arr.map(num => num * 2);And finally, this is how you could use an arrow function in your code: arr.forEach((_value, i) => {
// Function body goes here
});Also note how I called the first parameter There was a problem hiding this comment. ok, I think I got it at least for the first part. This short syntax for functions is easy, because you declare a variables value to the result of a function one evokes with a set of parameters like:
But using the same syntax just to define a function on to parameters without a result being assigned to a variable outside of it. Intuitively I would write it somehow that inside the checkEuler function the Something like: const isApprox = arr.forEach(( _value, i) => {
[...] // here is the calculation of the solution variable A which gets compared later on with threshold B
if ( A > B) {
[...]
return (A > B) // returning the logical value of the check here, but I can't tell if this valid
}
});If this would somehow be possible, then we are saving at least one line of code there. Because Edit: I see a problem with this procedure: If I felt smart for a little moment in time. |
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| const solution = Math.exp(-3 * time_step * i); | ||
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| if (Math.abs(arr[i] - solution) > threshold) { | ||
| console.log(arr[i], solution); | ||
| is_approx = false; | ||
| } | ||
| }); | ||
| return is_approx; | ||
| } | ||
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| function main() { | ||
| const time_step = 0.01; | ||
| const threshold = 0.01; | ||
| const n = 100; | ||
| var euler_result = forwardEuler(time_step, n); | ||
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There was a problem hiding this comment. You changed
function foo() {
// <- This is where JavaScript moves the var declaration
if (true) {
var bar; // JavaScript moves this declaration to the top of the function and outside of the block
let baz;
}
}So in case 1 |
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| var check_result = checkEuler(euler_result, time_step, threshold); | ||
| console.log(check_result); | ||
| } | ||
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| main(); | ||
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What was already said about snake_case vs. camelCase also applies to variables. This should be
timeStep. The same goes foris_approx,euler_resultandcheck_resultfurther down.