Node.js formatted console output - node.js

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?

Answer 1

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
// }

Answer 2

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

Answer 3

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

Answer 4

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.

Answer 5

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

Answer 6

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/

Answer 7

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

Answer 8

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" ' │
└─────────────────┴────────────────────────────────────────────────────────────────────────────────────────┘