locutus
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Locutus other languages' standard libraries to JavaScript for fun and educational purposes
109 lines (108 loc) • 3.31 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
exports.Format = Format;
const GO_LAYOUT_TOKENS = [
'Z07:00',
'-07:00',
'-0700',
'2006',
'PM',
'pm',
'15',
'06',
'01',
'02',
'03',
'04',
'05',
'1',
'2',
'3',
];
const pad2 = (value) => String(value).padStart(2, '0');
const formatToken = (token, date) => {
const year = date.getUTCFullYear();
const month = date.getUTCMonth() + 1;
const day = date.getUTCDate();
const hour24 = date.getUTCHours();
const hour12 = hour24 % 12 || 12;
switch (token) {
case '2006':
return String(year);
case '06':
return pad2(year % 100);
case '01':
return pad2(month);
case '1':
return String(month);
case '02':
return pad2(day);
case '2':
return String(day);
case '15':
return pad2(hour24);
case '03':
return pad2(hour12);
case '3':
return String(hour12);
case '04':
return pad2(date.getUTCMinutes());
case '05':
return pad2(date.getUTCSeconds());
case 'PM':
return hour24 >= 12 ? 'PM' : 'AM';
case 'pm':
return hour24 >= 12 ? 'pm' : 'am';
case '-0700':
return '+0000';
case '-07:00':
return '+00:00';
case 'Z07:00':
return 'Z';
default:
return token;
}
};
const toUtcDate = (value) => {
const date = value instanceof Date ? new Date(value.getTime()) : new Date(value);
if (Number.isNaN(date.getTime())) {
throw new TypeError('Format(): invalid date input');
}
return date;
};
const isTokenAt = (layout, index) => GO_LAYOUT_TOKENS.find((token) => layout.startsWith(token, index));
function Format(value, layout) {
// discuss at: https://locutus.io/golang/time/Format
// parity verified: Go 1.23
// original by: Kevin van Zonneveld (https://kvz.io)
// note 1: Supports a focused subset of Go layout tokens and formats in UTC for deterministic output.
// note 1: Unsupported layout markers are treated as literals.
// example 1: Format('2026-03-03T13:14:15.000Z', '2006-01-02')
// returns 1: '2026-03-03'
// example 2: Format('2026-03-03T13:14:15.000Z', '15:04:05')
// returns 2: '13:14:15'
// example 3: Format('2026-03-03T13:14:15.000Z', '01/02/06 03:04 PM')
// returns 3: '03/03/26 01:14 PM'
// example 4: Format('2026-03-03T13:14:15.000Z', 'Z07:00')
// returns 4: 'Z'
// example 5: Format('2026-03-03T13:14:15.000Z', '-07:00')
// returns 5: '+00:00'
const date = toUtcDate(value);
const resolvedLayout = String(layout);
let result = '';
for (let i = 0; i < resolvedLayout.length;) {
const token = isTokenAt(resolvedLayout, i);
if (token) {
result += formatToken(token, date);
i += token.length;
continue;
}
const char = resolvedLayout[i];
if (char === undefined) {
break;
}
result += char;
i += 1;
}
return result;
}