A lightweight, flexible string transformation engine for JavaScript and TypeScript. Transform Engine enables dynamic string interpolation, inline expressions, and powerful formatting with a clean, customizable syntax.
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-
Inline Expressions: Use
{{ ... }}to embed dynamic expressions directly in your strings. - Built-in Methods: Perform calculations, string manipulations, and more with a rich set of built-in methods.
- Chained Formatters: Pipe results through formatters for advanced formatting.
- Customizable & Extensible: Easily extend with your own methods and formatters (API coming soon).
- Zero Dependencies: Lightweight and fast, suitable for any project.
- AI Generated, well formatted & well tested: Unit tested with automation testing and verified by humans. It is type safe, null safe.
npm install @js-utility/template-engineimport { TransformEngine } from '@js-utility/template-engine';
const input = 'Total: {{ sum:10:20 | currency "US":2 }}';
const output = TransformEngine(input, {});
console.log(output); // Total: $30.00Each placeholder follows this pattern:
{{ method:param1:param2 | formatter:param1:param2 }}
-
method: The function to execute (e.g.,
sum,row.name) - params: (Optional) Arguments to the method (numbers, strings, variables), separated by colons (:)
-
formatter: (Optional) Pipe output through a formatter (e.g.,
currency,capitalize) - formatParams: (Optional) Arguments to the formatter (numbers, strings, variables), separated by colons (:)
Examples:
{{ sum:2:3 }} => 5
{{ row.name | capitalize }} => John doe
{{ row.amount | currency 'US':2 }} => $1,234.57
{{ sum:10:20 | number 'US':1 }} => 30.0
{{ 0.25 | percentage 2 }} => 25.00%
| Function | Description |
|---|---|
| TransformEngine(text: string, context?: object, options?: object): string | Transforms the input string by evaluating all placeholders. |
| Name | Type | Description |
|---|---|---|
| text | string | The input string containing placeholders. |
| context | object | (Optional) Data object for expression resolution. |
| options | object | (Optional) Reference Resolution Parameter, that supports context format to key value pair for references. It is default to off. |
Returns:
string — The transformed string with all placeholders evaluated.
| Method | Description |
|---|---|
| sum | Adds all arguments |
| subtract | Subtracts numbers |
| avg | Returns average |
| min | Minimum value |
| max | Maximum value |
| count | Counts number of items |
| multiply | Multiplies all numbers |
| divide | Divides numbers |
| concat | Concatenates strings |
| mod | Modulo |
| pow | Exponentiation |
| abs | Absolute value |
| floor | Rounds down |
| ceil | Rounds up |
| sqrt | Square root |
| log | Natural logarithm |
| echo | Returns the first argument |
| length | Length of string or array |
| size | Alias of length |
| Formatter | Description |
|---|---|
| upper | Converts to uppercase |
| lower | Converts to lowercase |
| round | Rounds to nearest integer |
| number | Formats number with fraction points (e.g., number 'US':1:2) |
| date | Formats as date |
| currency | Formats as currency (e.g., currency "US":0:2 for country and decimals) |
| percentage | Formats as percent (e.g., percentage 0:2 for decimals) |
| json | Converts to JSON string |
| capitalize | Capitalizes the first letter |
| trim | Trims whitespace |
| length | Gets length of string or array |
| camel | Converts to camelCase |
| snake | Converts to snake_case |
| strip | Removes non-alphanumerics |
| prefix | Adds a prefix (e.g., prefix:"ID-") |
| suffix | Adds a suffix |
| repeat | Repeats a string (e.g., repeat:3) |
| title | Converts to Title Case |
Note:
-
currencyandnumberuse the same parameter structure:
formatter alpha_2_country_code:min_fraction:max_fraction-
alpha_2_country_code: e.g.,"US" -
min_fraction(optional): Minimum Number of decimal places. default to '0' -
max_fraction(optional): Maximum Number of decimal places. default to 'min_fraction'
-
const PLACEHOLDER_REGEX = /\{\{\s*([^\s|}]+)(?:\s+([^|}]*?))?(?:\s*\|\s*([^\s|}]+)(?:\s+([^}]*?))?)?\s*\}\}/g;- Supports:
{{ method args | formatter params }} - Flexible whitespace and quoted string arguments (
"...",'...')
TransformEngine('Hello {{ row.name | capitalize }}!', { row: { name: 'sarah' } });
// => Hello Sarah!
TransformEngine('Price: {{ sum 10:15 | currency "US":2 }}');
// => Price: $25.00
TransformEngine('{{ echo "hello world" | upper }}');
// => HELLO WORLD
TransformEngine('Value: {{ sum 1520.856:864.69 | currency "US":1 }}');
// => Value: $2,385.5
TransformEngine('Percent: {{ 0.8320 | percentage 1 }}');
// => Percent: 83.2%This package is built with full TypeScript support. All functions are type-safe, and type definitions are bundled, so you get autocomplete, inline documentation, and compile-time safety out of the box, no need to install @types.
This package is thoroughly tested using Jest, with a focus on correctness, edge cases, and null-safety.
This project is maintained privately. While direct contributions (e.g., pull requests or code changes) are not open to the public, feedback, suggestions, and issue reports are always welcome.
If you notice any bugs, edge cases, or have ideas for improvement, feel free to reach out or open an issue (if access is available). Your input helps make the package more robust and useful for everyone!
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Support as through :
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