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59 lines
2.4 KiB
59 lines
2.4 KiB
/**
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* Given a 2D array of strings, encodes them in tab-separated format.
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* Certain values are quoted; when quoted, internal quotes get doubled. The behavior attempts to
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* match Excel's tsv encoding and parsing when using copy-paste.
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*/
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export function tsvEncode(data: any[][]): string {
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return data.map(row => row.map(value => encode(value)).join("\t")).join("\n");
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}
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function encode(rawValue: any): string {
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// For encoding-decoding symmetry, we should also encode any values that start with '"',
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// but neither Excel nor Google Sheets do it. They both decode such values to something
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// different than what produced them (e.g. `"foo""bar"` is encoded into `"foo""bar"`, and
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// that is decoded into `foo"bar`).
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const value: string = typeof rawValue === 'string' ? rawValue :
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(rawValue == null ? "" : String(rawValue));
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if (value.includes("\t") || value.includes("\n")) {
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return '"' + value.replace(/"/g, '""') + '"';
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}
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return value;
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}
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/**
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* Given a tab-separated string, decodes it and returns a 2D array of strings.
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* TODO: This does not yet deal with Windows line endings (\r or \r\n).
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*/
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export function tsvDecode(tsvString: string): string[][] {
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const lines: string[][] = [];
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let row: string[] = [];
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// This is a complex regexp but it does the job of a lot of parsing code. Here are the parts:
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// A: [^\t\n]* Sequence of character that does not require the field to get quoted.
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// B: ([^"]*"")*[^"]* Sequence of characters containing all double-quotes in pairs (i.e. `""`)
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// C: "B"(?!") Quoted sequence, with all double-quotes inside paired up, and ending in a single quote.
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// D: C?A A value for one field, a relaxation of C|A (to cope with not-quite expected data)
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// E: D(\t|\n|$) Field value with field, line, or file terminator.
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const fieldRegexp = /(("([^"]*"")*[^"]*"(?!"))?[^\t\n]*)(\t|\n|$)/g;
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for (;;) {
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const m = fieldRegexp.exec(tsvString);
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if (!m) { break; }
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const sep = m[4];
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let value = m[1];
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if (value.startsWith('"')) {
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// It's a quoted value, so doubled-up quotes should became individual quotes, and individual
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// quotes should be removed.
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value = value.replace(/"([^"]*"")*[^"]*"(?!")/, q => q.slice(1, -1).replace(/""/g, '"'));
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}
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row.push(value);
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if (sep !== '\t') {
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lines.push(row);
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row = [];
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if (sep === '') {
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break;
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}
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}
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}
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return lines;
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}
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