PreFormat Column Value

For information on the annotation,2016:column-display specifics you can refer this annotations document

The annotation is represented as follows:

       "pre_format": {
           "format": "%t",
           "bool_true_value": "YES",
           "bool_false_value": "NOPE",

The pre_format parameter of the annotation accepts an object with 3 properties.

  1. format: (MANDATORY) It is the actual formatting string which is passed the column value and is mandatory. It uses POSIX standard to format strings.
  2. bool_true_value and bool_false_value: (OPTIONAL) These properties help to swap values of boolean true and false with relevant string values.


The format string uses following syntax:


The placeholders in the format string are marked by % and are followed by one or more of these elements, in this order:

Flags field:

The Flags field can be zero or more (in any order) of:

- (minus) Left-align the output of this placeholder. (The default is to right-align the output.).
          This is used in conjunction with width field.

+ (plus)  Prepends a plus for positive signed-numeric types. positive = +, negative = -
          (The default doesn't prepend anything in front of positive numbers.)

0 (zero)  When the 'width' option is specified, prepends zeros for numeric types. (The default prepends spaces.)
          For example, printf("%2X",3) produces  3, while printf("%02X",3) produces in 03.

' (quote) It separates numeric types by thousands using a comma (,) or other characters according to localization

#{char}   An optional padding specifier that says what character to use for padding (if specified).
          Possible values are any other character precedeed by a # (hash). print("%#_5d",10) produces ___10

Width field

The Width field specifies a minimum number of characters to output, and is typically used to pad fixed-width fields, where the fields would otherwise be smaller, although it does not cause truncation of oversized fields.

For example, printf("%*d", 5, 10) will result in " 10" being printed, with a total width of 5 characters.

Though not part of the width field, a leading zero is interpreted as the zero-padding flag mentioned above, and a negative value is treated as the positive value in conjunction with the left-alignment flag mentioned above.

When used with the j (JSON) type specifier, the padding length specifies the tab size used for indentation.

Precision Field

The Precision field usually specifies a maximum limit on the output, depending on the particular formatting type.

For floating point numeric types, it specifies the number of digits to the right of the decimal point that the output should be rounded.

For the string type, it limits the number of characters that should be output, after which the string is truncated.

For example, printf("%.3s", 3.42134) will result in 3.421 being printed.

Type Field

It can be any of:

% — yields a literal % character
b — yields an integer as a binary number
c — yields an integer as the character with that ASCII value
d or i — yields an integer as a signed decimal number
e — yields a float using scientific notation
u — yields an integer as an unsigned decimal number
f — yields a float as is; see notes on precision above
o — yields an integer as an octal number
s — yields a string as is
t — yields true or false
X — yields an integer as a hexadecimal number (upper-case)
j — yields a JavaScript object or array as a JSON encoded string

Named arguments:

Format strings may contain replacement fields rather than positional placeholders. Instead of referring to a certain argument, you can now refer to a certain key within an object. Replacement fields are surrounded by rounded parentheses - ( and ) - and begin with a keyword that refers to a key:

value => { name: 'Dolly' }

format =>'Hello %(name)s'

Output => Hello Dolly

Keywords in replacement fields can be optionally followed by any number of keywords or indexes:

value => [
    {name: 'Dolly'},
    {name: 'Molly'},
    {name: 'Polly'},

format => 'Hello %(users[0].name)s, %(users[1].name)s and %(users[2].name)s'

output =>


Expression Input Output
'%%' '%'
'%b' 2 '10'
'%c' 65 'A'
'%d' 2 '2'
'%i' 2 '2'
'%d' '2' '2'
'%i' '2' '2'
'%j' { "foo": "bar" } '{"foo":"bar"}'
'%j' ["foo", "bar"] '["foo","bar"]'
'%e' 2 '2e+0'
'%u' 2 '2'
'%u' -2 '4294967294'
'%f' 2.2 '2.2'
'%g' 3.141592653589793 '3.141592653589793'
'%o' 8 '10'
'%o' -8 '37777777770'
'%s' '%s' '%s'
'%X' 255 'FF'
'%X' -255 'FFFFFF01'
'Hello %(who)s!' { who: 'world' } 'Hello world!'
'%t' true 'true'
'%.1t' true 't'
'%t' 'true' 'true'
'%t' 1 'true'
'%t' false 'false'
'%.1t' false 'f'
'%t' '' 'false'
'%t' 0 'false'
'%d' 2 '2'
'%d' -2 '-2'
'%+d' 2 '+2'
'%+d' -2 '-2'
'%i' 2 '2'
'%i' -2 '-2'
'%+i' 2 '+2'
'%+i' -2 '-2'
'%f' 2.2 '2.2'
'%f' -2.2 '-2.2'
'%+f' 2.2 '+2.2'
'%+f' -2.2 '-2.2'
'%+.1f' -2.34 '-2.3'
'%+.1f' -0.01 '-0.0'
'%.6g' 3.141592653589793 '3.14159'
'%.3g' 3.141592653589793 '3.14'
'%.1g' 3.141592653589793 '3'
'%+010d' -123 '-000000123'
'%+#_10d' -123 '__-123'
'%f' -234.34 '-234.34'
'%05d' -2 '-0002'
'%05i' -2 '-0002'
'%5s' '<' ' <'
'%05s' '<' '0000<'
'%#_5s' '<' '____<'
'%-5s' '>' '> '
'%0-5s' '>' '>0000'
'%#_-5s' '>' '>____'
'%5s' 'xxxxxx' 'xxxxxx'
'%02u' 1234 '1234'
'%8.3f' -10.23456 ' -10.235'
'%f %s' -12.34 '-12.34 xxx'
'%2j' { "foo": "bar" } '{\n "foo":"bar"\n}'
'%2j' ["foo", "bar"] '[\n "foo",\n "bar"\n]'
'%.1f' 2.345 '2.3'
'%5.5s' 'xxxxxx' 'xxxxx'
'%5.1s' 'xxxxxx' ' x'
%'15.3f 10000.23456 ' 10,000.235'
%'15d 12345668 ' 12,345,668'

Example for using json keys in format

Format => "My name is %(name)s. My age is %(age)d years and I study at %( located in %(school.location)s. My GPA is %(grade).2f"

Value => { name: 'John Doe', age: 24, school: { name: 'USC',  location: 'Los Angeles CA' }, grade: 3.9822 })

Output => 'My name is John Doe. My age is 24 years and I study at USC located in Los Angeles CA. My GPA is 3.98'

Syntax for Dates and Timestamps

String + Formats as defined in moment.js documentation.

Most common Year, Month, and Day tokens:

Input Example Description
YYYY 2014 4 digit year
YY 14 2 digit year
M MM 1..12 Month number
MMM MMMM Jan..December Month name in locale
D DD 1..31 Day of month
Do 1st..31st Day of month with ordinal
DDD DDDD 1..365 Day of year

Most common Hour, minute, second, millisecond, and offset tokens:

Input Example Description
H HH 0..23 Hours (24 hour time)
h hh 1..12 Hours (12 hour time used with a A.)
k kk 1..24 Hours (24 hour time from 1 to 24)
a A am pm Post or ante meridiem (Note the one character a p are also considered valid)
m mm 0..59 Minutes
s ss 0..59 Seconds
S SS SSS 0..999 Fractional seconds
Z ZZ +12:00 Offset from UTC as +-HH:mm, +-HHmm, or Z