Expressinish

An expression-parsing middle ground library between find-and-replace and full js access

Installing

npm install --save expressionish

API

You can find the full API documentation at [TODO: add link]

import { evaluate } from 'expressionish';

const variables = new Map();
variables.set('sum', {
    evaluate: async (meta, ...args) => {
        return args.reduce((prev, curr) => prev + Number(curr), 0)
    }
});

await evaluate({
    variables,
    expression: '\$sum[1,2,3]: $sum[1,2,3]'
}) // "$sum[1,2,3]: 6'

Syntax

You can find the full Syntax documentation at [TODO: add link]

Text

Any text that is not seen as having significance is treated as plain text.

Concatenation is done simply by mixing insignificant and significant sequences: v$var is evaluated to "v" followed by result of evaluating $var

Character escapes

Character escapes treat characters that may have potential significance as literl text instead.

• \\ - backslash
• \" - quote
• \$ - dollar sign
• \[ - opening bracket
• \, - comma
• \] - closing brackets
• \r - carriage return
• \n - line feed
• \t - tab

Double-Quoted Text

Text contained with in double quotes is treated as plain-text with the exception of character-escapes(of which get evaluated)

Double Backtick Text

Text contained within double backtick's is treated as plain-text with the exception of Variables

Variables & Lookups

Variables are the power behind expressions. They can take no arguments or a slew of them! An argument can even be an expression of itself, containing variables and the like!

Variables take the format of:

"$" + [<lookup_prefix>] + <name> + [ "[" + <arg> + ["," + <arg>]... + "]" ]

Examples:

$name - variable
$name[1] - variable with one argument
$name[1,2,3] - variable with multiple arguments

$&name - variable lookup
$&name[1] - variable lookup with one argument
$&name[1,2,3] - variable lookup with multiple arguments

When it comes to arguments, leading/trailing whitespace is insignificant

These are all the same
$name[1]
$name[ 1]
$name[ 1 ]
$name[
    1
]