Node.js formatted console output

Question

Is there a simple built-in way to output formatted data to console in Node.js?

Indent, align field to left or right, add leading zeros?

I don't know about any of those, but similar one is `colors` and it can format the strings outputted e.g. `"Green colour".green` — Matej, Nov 07 '13 at 13:53
I'm assuming you're asking to do something like `console.setup({ color: 'green', prepend: '0000' })`, but already built in? You could make your own logging method or override the `stdout.write` method (although people suggest not overriding native functions). — matth, Nov 07 '13 at 14:35
I was thinking about `printf()` with various handy format modifiers to the output string. — exebook, Nov 07 '13 at 17:13
The answers below are good. In addition though, if you also want to add automatic colors to your standard Node.js output, check out [manakin](https://github.com/vitaly-t/manakin). — vitaly-t, Dec 02 '16 at 12:24

score 74 · Accepted Answer · edited Sep 25 '17 at 10:50

74

Two new(1) built in methods String.Prototype.padStart and String.Prototype.padEnd were introduced in ES2017 (ES8) which perform the required padding functions.

(1) node >= 8.2.1 (or >= 7.5.0 if run with the --harmony flag)

Examples from the mdn page:

'abc'.padStart(10);         // "       abc"
'abc'.padStart(10, "foo");  // "foofoofabc"
'abc'.padStart(6,"123465"); // "123abc"
'abc'.padStart(8, "0");     // "00000abc"
'abc'.padStart(1);          // "abc" 

'abc'.padEnd(10);          // "abc       "
'abc'.padEnd(10, "foo");   // "abcfoofoof"
'abc'.padEnd(6, "123456"); // "abc123"
'abc'.padEnd(1);           // "abc"

For indenting a json onto the console try using JSON.stringify. The third parameter provides the indention required.

JSON.stringify({ a:1, b:2, c:3 }, null, 4);
// {
//    "a": 1,
//    "b": 2,
//    "c": 3
// }

edited Sep 25 '17 at 10:50

exebook

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answered Sep 08 '17 at 05:18

TheChetan

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May be worthwhile to note that this is supported only in node >= 8.2.1 (or >= 7.5.0 if run with the `--harmony` flag) since it is rather recent yet. – Semicolon Sep 09 '17 at 05:37
This is working for me on v8.1.2 even without the flag. – Jakub Macháček Jan 04 '18 at 20:50
Don't forget to use .toString() if you're not seeing this work. – mdhansen Feb 05 '20 at 22:49

score 34 · Answer 2 · answered Nov 28 '18 at 13:50

If the data is tabular, then the simplest way would be to do it with console.table

https://nodejs.org/dist/latest-v10.x/docs/api/console.html#console_console_table_tabulardata_properties

This is the code.

console.table(
  COMMANDS.map(command => {
    return {
      "Long Option": command.long_option,
      "Short Option": command.short_option,
      Description: command.description
    };
  })
);

You don't need external libraries for it. Here is sample output. You only need to pass an array object.

Not only in Nodejs, but it also works in chrome.

https://developer.mozilla.org/en-US/docs/Web/API/Console/table

Any way to left indent the contents of column? It defaults to center alignment. — Gaurang Patel, Aug 29 '20 at 00:12

WiredPrairie · Answer 3 · 2015-12-18T15:01:25.763

28

There's nothing built into NodeJS to do this. The "closest" you'd come is util.format, which still doesn't do much unfortunately (reference).

You'll need to look into other modules to provide a richer formatting experience. For example: sprintf.

Sprintf-js allows both positional (0, 1, 2) arguments and named arguments.

A few examples of padding and alignment:

var sprintf=require("sprintf-js").sprintf;

console.log(sprintf("Space Padded => %10.2f", 123.4567));
console.log(sprintf("    _ Padded => %'_10.2f", 123.4567));
console.log(sprintf("    0 Padded => %010.2f", 123.4567));
console.log(sprintf(" Left align => %-10.2f", 123.4567));

Results:

Space Padded =>     123.46
    _ Padded => ____123.46
    0 Padded => 0000123.46
 Left align => 123.46

edited Dec 18 '15 at 15:01

answered Nov 07 '13 at 14:42

WiredPrairie

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`util.format` is better than nothing. But, not much better. :) If it was just part of `console.log` ... then it would make more sense. – WiredPrairie Nov 07 '13 at 17:35
I added a few examples to round out the answer. – WiredPrairie Nov 07 '13 at 17:47
how do i pass a string? – chovy Sep 14 '16 at 07:09
@chovy-the docs have a lot of examples and I'd suggest you start there. – WiredPrairie Sep 14 '16 at 10:35

score 7 · Answer 4 · answered Nov 07 '13 at 14:44

7

If you have simpler needs you can look into util.format. It can generate string from various parameters. If you want printf like formatting you can use either sprintf package or sprintf-js package.

answered Nov 07 '13 at 14:44

user568109

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Seems just like my answer? :) – WiredPrairie Nov 07 '13 at 14:46
Yeah, just few minutes late. – user568109 Nov 07 '13 at 14:49

score 3 · Answer 5 · answered Oct 06 '15 at 13:07

3

Take a look at Log4JS, which is an attempt at a functional port of Log4j

answered Oct 06 '15 at 13:07

Lee Goddard

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score 3 · Answer 6 · edited Sep 07 '17 at 07:19

3

You might also like string-kit and terminal-kit.

https://www.npmjs.com/package/string-kit

https://www.npmjs.com/package/terminal-kit

https://blog.soulserv.net/terminal-friendly-application-with-node-js-part-ii-moving-and-editing/

edited Sep 07 '17 at 07:19

cascading-style

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answered Mar 15 '17 at 04:15

jjstiff

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Hey! Welcome to Stack Overflow! Although the link may contain the answer to the question, make sure you provide the essential information on your answer, so that if that link is ever taken down, the answer is still valid. Thanks! – Matheus Avellar Mar 15 '17 at 04:38

score 2 · Answer 7 · answered Apr 30 '21 at 01:47

2

If I combine util.format and "".padStart/"".padEnd together,as described in posts above, then I get what I wated:

> console.log(util.format("%s%s","Name:".padEnd(10), "John Wall"))
Name:     John Wall

answered Apr 30 '21 at 01:47

spikeyang

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score 1 · Answer 8 · answered Sep 10 '21 at 21:00

A version of console.table for NodeJS with align.

⚠ This is only for console version! ⚠

/**
 * @param {NonNullable<{
 *    [key: string]: string
 *  }>} data
 */
const consoleTable = (data) => {
  if (typeof data === 'object') {
    const e = Object.entries(data);
    let kl = 0;
    let vl = 0;

    for (const [k, v] of e) {
      if (k.length > kl) {
        kl = k.length;
      }

      const s = JSON.stringify(v);
      const l = s ? s.length : 0;

      if (l > vl) {
        vl = l;
      }
    }

    /** @type {{ [key: string] : string }} */
    const result = {};

    for (const [k, v] of e) {
      const s = JSON.stringify(v);
      result[k.padStart(kl)] = s ? s.padEnd(vl) : v;
    }

    console.table(result);
  } else {
    console.table(data);
  }
};

Output example:

┌─────────────────┬────────────────────────────────────────────────────────────────────────────────────────┐
│     (index)     │                                         Values                                         │
├─────────────────┼────────────────────────────────────────────────────────────────────────────────────────┤
│     CONFIG_FILE │ '"/Users/ecuomo/projects/zzzzz/xxxxxxxx/tttttttttt-web/jjjjjjjjjj-commons/config.env"' │
│        NODE_ENV │ '"development"                                                                       ' │
│         APP_ENV │ '"local-dev-edu"                                                                     ' │
│     APP_VERSION │ '"0-local-ecuomo"                                                                    ' │
│        BASE_URL │ '"http://localhost:3000"                                                             ' │
│    CDN_BASE_URL │ '"http://localhost:3000/static"                                                      ' │
│    API_BASE_URL │ '"http://localhost:3000/api"                                                         ' │
│           MONGO │ '"mongodb://mongo:27017/xxxxxxxxxxprod"                                              ' │
│      MYSQL_HOST │ '"mysql"                                                                             ' │
│      MYSQL_PORT │ '3306                                                                                ' │
│    MYSQL_DB_ETL │ '"xxxxxxxxxx_etl"                                                                    ' │
│  MYSQL_DB_STATS │ '"xxxxxxxxxx_stats"                                                                  ' │
│ MYSQL_DB_ZAPIER │ '"xxxxxxxxxx_yyyyyy"                                                                 ' │
│   POSTGRES_HOST │ '"postgres"                                                                          ' │
│   POSTGRES_PORT │ '5432                                                                                ' │
│     POSTGRES_DB │ '"xxxxxxxxxx"                                                                        ' │
│      REDIS_HOST │ '"redis"                                                                             ' │
│      REDIS_PORT │ '"6379"                                                                              ' │
│    REDIS_MASTER │                                       undefined                                        │
│      REDIS_MODE │ '"single"                                                                            ' │
└─────────────────┴────────────────────────────────────────────────────────────────────────────────────────┘

Node.js formatted console output

8 Answers8

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