Documentation Index
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Obsidian Bases provides a rich set of built-in functions that can be called inside formula expressions and filter strings. Functions are organized by the type they operate on — global functions are called standalone, while type-specific functions are called as methods on a value using dot notation (e.g. file.ctime.format("YYYY-MM-DD") or file.tags.contains("project")). This page documents every built-in function available, organized by type.
Global Functions
Global functions are called directly by name without a receiver object. They are available everywhere an expression is valid — in formulas:, in filter strings, and in summary expressions.
| Function | Signature | Description |
|---|
date() | date(string): date | Parse a string to a date. Format: YYYY-MM-DD HH:mm:ss |
duration() | duration(string): duration | Parse a duration string (e.g. "1d", "2 weeks") |
now() | now(): date | Current date and time |
today() | today(): date | Current date with time set to 00:00:00 |
if() | if(condition, trueResult, falseResult?) | Conditional expression; falseResult defaults to empty |
min() | min(n1, n2, ...): number | Returns the smallest of the supplied numbers |
max() | max(n1, n2, ...): number | Returns the largest of the supplied numbers |
number() | number(any): number | Convert a value to a number |
link() | link(path, display?): Link | Create a link from a path, with optional display text |
list() | list(element): List | Wrap a value in a list if it is not already one |
file() | file(path): file | Get a file object for the given vault path |
image() | image(path): image | Create an image value for rendering |
icon() | icon(name): icon | Reference a Lucide icon by name |
html() | html(string): html | Render a string as raw HTML |
escapeHTML() | escapeHTML(string): string | Escape HTML special characters in a string |
Any Type Functions
These functions are available on any value, regardless of its type.
| Function | Signature | Description |
|---|
isTruthy() | any.isTruthy(): boolean | Coerce the value to a boolean |
isType() | any.isType(type): boolean | Check whether the value is of the specified type |
toString() | any.toString(): string | Convert the value to a string |
Date Functions
Date values expose both fields (accessed with dot notation, no parentheses) and functions (called with parentheses).
Date fields:
| Field | Type | Description |
|---|
date.year | Number | Four-digit year |
date.month | Number | Month (1–12) |
date.day | Number | Day of the month (1–31) |
date.hour | Number | Hour (0–23) |
date.minute | Number | Minute (0–59) |
date.second | Number | Second (0–59) |
date.millisecond | Number | Millisecond (0–999) |
| Function | Signature | Description |
|---|
date() | date.date(): date | Strip the time portion, returning midnight on that date |
format() | date.format(string): string | Format using a Moment.js pattern (e.g. "YYYY-MM-DD", "dddd") |
time() | date.time(): string | Get the time portion as a string |
relative() | date.relative(): string | Human-readable relative time (e.g. “3 days ago”) |
isEmpty() | date.isEmpty(): boolean | Always returns false for date values |
Duration Type
A Duration is returned when you subtract two dates. It has its own set of numeric fields and does not share the numeric functions available on plain numbers.
Duration fields:
| Field | Type | Description |
|---|
duration.days | Number | Total days in the duration |
duration.hours | Number | Total hours in the duration |
duration.minutes | Number | Total minutes in the duration |
duration.seconds | Number | Total seconds in the duration |
duration.milliseconds | Number | Total milliseconds in the duration |
Duration does not support .round(), .floor(), or .ceil() directly. You must first access a numeric field (such as .days), and then call number functions on the resulting number.# ✅ CORRECT — access .days first, then round
"(now() - file.ctime).days.round(0)"
# ✅ CORRECT — access .hours first
"(now() - file.ctime).hours.round(0)"
# ❌ WRONG — Duration does not support .round() directly
"(now() - file.ctime).round(0)"
# ❌ WRONG — Duration does not support division
"((date(due) - today()) / 86400000).round(0)"
Date Arithmetic
Dates support addition and subtraction of duration strings. Subtracting two dates returns a Duration (see above).
# Add a duration string to a date
"date + \"1M\"" # Add 1 month
"date - \"2h\"" # Subtract 2 hours
"now() + \"1 day\"" # Tomorrow
"today() + \"7d\"" # A week from today
# Subtract dates — returns Duration type
"now() - file.ctime" # Returns Duration
"(now() - file.ctime).days" # Get days as number
"(now() - file.ctime).hours" # Get hours as number
# Complex duration arithmetic
"now() + (duration('1d') * 2)"
| Unit | Abbreviations |
|---|
| Years | y, year, years |
| Months | M, month, months |
| Weeks | w, week, weeks |
| Days | d, day, days |
| Hours | h, hour, hours |
| Minutes | m, minute, minutes |
| Seconds | s, second, seconds |
String Functions
String values expose a length field and a suite of method functions.
String field:
| Field | Type | Description |
|---|
string.length | Number | Number of characters in the string |
| Function | Signature | Description |
|---|
contains() | string.contains(value): boolean | Check whether the string contains a substring |
containsAll() | string.containsAll(...values): boolean | Check whether all substrings are present |
containsAny() | string.containsAny(...values): boolean | Check whether any substring is present |
startsWith() | string.startsWith(query): boolean | Check whether the string starts with the query |
endsWith() | string.endsWith(query): boolean | Check whether the string ends with the query |
isEmpty() | string.isEmpty(): boolean | Returns true if the string is empty or not present |
lower() | string.lower(): string | Convert to lowercase |
title() | string.title(): string | Convert to Title Case |
trim() | string.trim(): string | Remove leading and trailing whitespace |
replace() | string.replace(pattern, replacement): string | Replace a pattern with a replacement string |
repeat() | string.repeat(count): string | Repeat the string a given number of times |
reverse() | string.reverse(): string | Reverse the characters in the string |
slice() | string.slice(start, end?): string | Extract a substring by character index |
split() | string.split(separator, n?): list | Split the string into a list on a separator |
Number Functions
| Function | Signature | Description |
|---|
abs() | number.abs(): number | Absolute value |
ceil() | number.ceil(): number | Round up to the nearest integer |
floor() | number.floor(): number | Round down to the nearest integer |
round() | number.round(digits?): number | Round to the specified number of decimal digits |
toFixed() | number.toFixed(precision): string | Format in fixed-point notation as a string |
isEmpty() | number.isEmpty(): boolean | Returns true if the number is not present |
List Functions
List values expose a length field and a comprehensive set of method functions for querying and transforming lists.
List field:
| Field | Type | Description |
|---|
list.length | Number | Number of elements in the list |
| Function | Signature | Description |
|---|
contains() | list.contains(value): boolean | Check whether the list contains the value |
containsAll() | list.containsAll(...values): boolean | Check whether all values are in the list |
containsAny() | list.containsAny(...values): boolean | Check whether any value is in the list |
filter() | list.filter(expression): list | Filter elements by a boolean expression |
map() | list.map(expression): list | Transform each element with an expression |
reduce() | list.reduce(expression, initial): any | Reduce the list to a single value |
flat() | list.flat(): list | Flatten a nested list of lists into a single list |
join() | list.join(separator): string | Join all elements into a string with a separator |
reverse() | list.reverse(): list | Reverse the order of elements |
slice() | list.slice(start, end?): list | Extract a sub-list by index |
sort() | list.sort(): list | Sort elements in ascending order |
unique() | list.unique(): list | Remove duplicate elements |
isEmpty() | list.isEmpty(): boolean | Returns true if the list has no elements |
The list.filter(), list.map(), and list.reduce() functions use the special iteration variables value (the current element) and index (the zero-based position) inside the expression. list.reduce() additionally exposes acc for the accumulator.# Filter to tags that start with "project/"
'file.tags.filter(value.startsWith("project/"))'
# Map to uppercase
'file.tags.map(value.title())'
# Reduce to a comma-separated string
'file.tags.reduce(acc + ", " + value, "")'
File Functions
These functions are called as methods on a file object — either the implicit file built-in for the current note, or a file object retrieved with the global file() function.
| Function | Signature | Description |
|---|
asLink() | file.asLink(display?): Link | Convert the file to a link, with optional display text |
hasLink() | file.hasLink(otherFile): boolean | Returns true if the file contains a link to the specified file |
hasTag() | file.hasTag(...tags): boolean | Returns true if the file has any of the specified tags |
hasProperty() | file.hasProperty(name): boolean | Returns true if the file’s frontmatter contains the property |
inFolder() | file.inFolder(folder): boolean | Returns true if the file is in the specified folder or any subfolder |
Link Functions
These functions are called on a Link value (created by link() or file.asLink()).
| Function | Signature | Description |
|---|
asFile() | link.asFile(): file | Get the file object that the link points to |
linksTo() | link.linksTo(file): boolean | Returns true if the link points to the specified file |
Object Functions
These functions are called on object values, such as file.properties (all frontmatter as an object).
| Function | Signature | Description |
|---|
isEmpty() | object.isEmpty(): boolean | Returns true if the object has no properties |
keys() | object.keys(): list | Returns a list of the object’s property names |
values() | object.values(): list | Returns a list of the object’s property values |
Regular Expression Functions
Regular expressions can be written inline using JavaScript regex literal syntax (/pattern/) and matched against strings.
| Function | Signature | Description |
|---|
matches() | regexp.matches(string): boolean | Returns true if the regex matches the string |
# Match only files whose basename is a date (YYYY-MM-DD)
filters: '/^\d{4}-\d{2}-\d{2}$/.matches(file.basename)'
# Match files whose name contains a four-digit year
filters: '/\d{4}/.matches(file.name)'