nodeJS util.format passing an array

Question

I am using util.format to format a string like this:

util.format('My name is %s %s', ['John', 'Smith']);

The fact that the second parameter is an array: ['John', 'Smith'], prevents my code from replacing the second %s. But i need it to be an array because I don't know the exact number of the arguments that the string might have.

Do you have any solution to my problem? Thank's in advance.

EDIT: The string that contains the placeholders is not a predefined static string. I read it from a file so the placeholders might be anywhere in the string. For the same reason I also don't know the number of placeholders.

jonrsharpe · Accepted Answer · 2025-02-09 16:42:47Z

13

You can make use of JavaScript's Function.prototype.apply to pass in arguments to a function from an Array source. This could look like

util.format.apply(util,['My name is %s %s','John', 'Smith']);

Of course you would need to .unshift() your placeholder string into that array as well beforehand.

edited Feb 9 at 16:42

jonrsharpe

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answered May 14, 2014 at 10:44

jAndy

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3 Comments

Bobos Over a year ago

The string that contains the placeholders is not a predefined static string. I read it from a file so the placeholders might be anywhere in the string. For the same reason i don't know the number of placeholders too.

jAndy Over a year ago

@Bobos Updated. Hope that helps.

Bobos Over a year ago

Great answer! Thank's! It seems that I need to better learn javascript ;)

Evert · Accepted Answer · 2025-02-09 17:04:14Z

1

You could also use ...:

util.format('My name is %s %s', ...['John', 'Smith']);

This also works with variables:

util.format('My name is %s %s', ...myArray);

answered Feb 9 at 17:04

Evert

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Comments

Abraham · Accepted Answer · 2014-05-14 11:00:51Z

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Do a for-each loop for every string object in table and replace every time one %s. (for example ['John', 'Smith'] has 2 strings)

answered May 14, 2014 at 11:00

Abraham

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