Formatting Strings

When you’re handling string data, you commonly need to format strings quickly. Node.js provides a rudimentary string formatting method in the util module that handles many string formatting needs. The util.format() function accepts a formatter string as the first argument and returns a formatted string. The following is the syntax for the format() method, where format is the formatter string and [...] represents the arguments that follow:

util.format(format, [...])

The format argument is a string that can contain zero or more placeholders. Each placeholder begins with a % character and is eventually replaced with the converted string value from its corresponding argument. The first formatter placeholder represents the second argument and so on. The following placeholders are supported:

%s: Specifies a string.

%d: Specifies a number (can be integer or float).

%j: Specifies a JSON stringifyable object.

%: If left empty, does not act as a placeholder.

Keep in mind the following when using format():

When there are not as many arguments as placeholders, the placeholders, such as %s, are not replaced. For example:

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util.format('%s = %s', 'Item1'), // 'Item1':%s'

When there are more arguments than placeholders, the extra arguments are converted to strings and concatenated with a space delimiter. For example

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util.format('%s = %s', 'Item1', 'Item2', 'Item3'), // 'Item1 = Item2 Item3'

If the first argument is not a format string, then util.format() converts each argument to a string, concatenates them together using a space delimiter, and then returns the concatenated string. For example:

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util.format(1, 2, 3); // '1 2 3'