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Fix InstaID precision without using bigint #259

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Fix InstaID precision without using bigint #259

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f1cbd55
Fix InstaID precision
Azureit Jan 25, 2022
0759949
Fix sum that in rare cases can output wrong value
Azureit Jan 26, 2022
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21 changes: 14 additions & 7 deletions src/ts/functions.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -55,18 +55,25 @@ export const shortcodeToDateString = (shortcode: string): string =>
shortcodeToInstaID(shortcode),
);

export const shortcodeToInstaID = (shortcode: string): number => {
export const shortcodeToInstaID = (shortcode: string): string => {
const alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_';
let id = 0;
const c_tri = 1000000000000;
let id_tri = 0;
let id_num = 0;
for (const char of shortcode) {
id = (id * 64) + alphabet.indexOf(char);
id_tri *= 64;
id_num = (id_num * 64) + alphabet.indexOf(char);
if (id_num >= c_tri) {
let quot = Math.floor(id_num / c_tri);
id_tri += quot;
id_num -= quot * c_tri;
}
}

return id;
return (id_tri.toString() + id_num.toString().padStart(c_tri.toString().length - 1, '0')).replace(/^0+/, "");
};

export const instaIDToTimestamp = (id: number) => {
const timestamp = (id / Math.pow(2, 23)) + 1314220021721;
export const instaIDToTimestamp = (id: string) => {
const timestamp = (Number(id) / Math.pow(2, 23)) + 1314220021721;

return new Date(timestamp).toLocaleString();
};