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utils.js
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utils.js
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const filterObject = (obj, callback) => {
return Object.fromEntries(Object.entries(obj).
filter(([key, val]) => callback(val, key)));
}
const pad = (n) => n<10 ? '0'+n : n;
const getTimestamp = () => {
const currentDate = new Date();
const date = pad(currentDate.getDate());
const month = pad(currentDate.getMonth() + 1);
const year = currentDate.getFullYear();
const hrs = pad(currentDate.getHours());
const mins = pad(currentDate.getMinutes());
const secs = pad(currentDate.getSeconds());
return `${date}.${month}.${year} ${hrs}.${mins}.${secs}`;
}
const msToTime = (ms) => {
let milliseconds = ms%1000;
let seconds = parseInt((ms/1000)%60);
let minutes = parseInt((ms/(1000*60))%60);
let hours = parseInt((ms/(1000*60*60))%24);
hours = pad(hours);
minutes = pad(minutes);
seconds = pad(seconds);
milliseconds = (milliseconds < 100) ? pad(milliseconds / 10) : milliseconds / 10;
return `${hours}:${minutes}:${seconds}.${milliseconds}`;
}
const seconds2HhMmSs = (seconds) => {
const secs = pad(Math.floor(seconds));
const mins = pad(Math.floor(secs / 60));
const hrs = pad(Math.floor(mins / 60));
return `${hrs}:${mins}:${secs}`;
}
const dedupe = (arr) => {
const deduped = [];
arr.forEach((elt) => {
if (!deduped.includes(elt)) {
deduped.push(elt);
}
});
return deduped;
}
const pushNew = (arr, elt) => {
if (!arr.includes(elt)) {
return arr.push(elt);
}
}
const repeatN = (n, iterator) => {
const accum = Array(Math.max(0, n));
for (let i = 0; i < n; i++) {
// Previously we just had iterator.call(), but passing in (this, i)
// gives code inside the iterator access to the current accumulator
// index, as in Array.map and Array.forEach.
accum[i] = iterator.call(this, i);
}
return accum;
}
const fill = (length, value) => repeatN(length, () => value);
const getLast = (arr) => arr.slice(-1)[0];
// With thanks to https://gomakethings.com/how-to-add-a-new-item-to-an-object-at-a-specific-position-with-vanilla-js/
const objectAddProperty = (obj, key, value, index) => {
// Create a temp object and index variable
var temp = {};
var i = 0;
// Loop through the original object
for (var prop in obj) {
if (obj.hasOwnProperty(prop)) {
// If the indexes match, add the new item
if (i === index && key && value) {
temp[key] = value;
}
// Add the current item in the loop to the temp obj
temp[prop] = obj[prop];
// Increase the count
i++;
}
}
// If no index, add to the end
if (!index && key && value) {
temp[key] = value;
}
return temp;
};
const range = (start, end) => {
const result = [];
for (let i = start; i <= end; i++) {
result.push(i);
}
return result;
}
// Conversion formulae obtained from: https://www.music.mcgill.ca/~gary/307/week1/node28.html.
const midiCps = (n) => {
return 440 * Math.pow(2, (n - 69) / 12);
}
const cpsMidi = (f) => {
return ~~(12 * (Math.log(f / 220.0) / Math.log(2.0)) + 57.01);
}
/*
const uInt8SampleToFloat32 = (sample) => {
return ( (sample / 128) - 1);
}
*/
// For this version see: https://github.com/mohayonao/get-float-time-domain-data/blob/master/lib/get-float-time-domain-data.js
// The seeming 'magic number' 0.0078125 is simply (2 / 256).
const uInt8SampleToFloat32 = (sample) => {
return (sample - 128) * 0.0078125;
}
const roundTo = (x, base=5) => base * Math.round(x / base);
const truncateTo = (x, base) => Math.floor(x / (base * 1.0)) * base;
const argMax = (arr, threshold=0) => {
const maxElt = Math.max.apply(null, arr);
if (maxElt > threshold) {
return arr.indexOf(maxElt);
}
}
// Numpy argsort.
// Adapted from https://stackoverflow.com/a/46622523/795131.
const argSort = (arr) => {
return arr.map((item, index) => [index, item])
.sort(([,arg1], [,arg2]) => arg1 - arg2)
.map(([item,]) => item);
}
const sum = (arr) => arr.reduce((a, b) => a + b, 0);
const mean = (arr) => sum(arr) / arr.length;
// Computes z-score normalisation, a normalisation
// strategy recommended for time series.
const zScore = (arr) => {
const arrMean = mean(arr);
const diffs = arr.map((elt) => (elt - arrMean) ** 2);
const stdDev = (sum(diffs) / arr.length) ** 0.5;
return arr.map((elt) => (elt - arrMean) / stdDev);
}
const zeros = (size) => repeatN(size, () => 0);
// https://quickref.me/swap-the-rows-and-columns-of-a-matrix
const transpose = (matrix) => matrix[0].map((col, i) => matrix.map((row) => row[i]));
const clamp = (x, min, max) => {
return Math.max(min, Math.min(x, max));
}
const rms = (values) => {
const sumOfSquares = values.reduce((sum, value) => {
return sum + Math.pow(value, 2);
}, 0);
return Math.sqrt(sumOfSquares / values.length);
}
module.exports = {
filterObject,
pad,
getTimestamp,
msToTime,
seconds2HhMmSs,
dedupe,
pushNew,
repeatN,
fill,
getLast,
objectAddProperty,
range,
midiCps,
cpsMidi,
uInt8SampleToFloat32,
roundTo,
truncateTo,
argMax,
argSort,
sum,
mean,
zScore,
zeros,
transpose,
clamp,
rms,
}