npm package discovery and stats viewer.

Discover Tips

  • General search

    [free text search, go nuts!]

  • Package details

    pkg:[package-name]

  • User packages

    @[username]

Sponsor

Optimize Toolset

I’ve always been into building performant and accessible sites, but lately I’ve been taking it extremely seriously. So much so that I’ve been building a tool to help me optimize and monitor the sites that I build to make sure that I’m making an attempt to offer the best experience to those who visit them. If you’re into performant, accessible and SEO friendly sites, you might like it too! You can check it out at Optimize Toolset.

About

Hi, 👋, I’m Ryan Hefner  and I built this site for me, and you! The goal of this site was to provide an easy way for me to check the stats on my npm packages, both for prioritizing issues and updates, and to give me a little kick in the pants to keep up on stuff.

As I was building it, I realized that I was actually using the tool to build the tool, and figured I might as well put this out there and hopefully others will find it to be a fast and useful way to search and browse npm packages as I have.

If you’re interested in other things I’m working on, follow me on Twitter or check out the open source projects I’ve been publishing on GitHub.

I am also working on a Twitter bot for this site to tweet the most popular, newest, random packages from npm. Please follow that account now and it will start sending out packages soon–ish.

Open Software & Tools

This site wouldn’t be possible without the immense generosity and tireless efforts from the people who make contributions to the world and share their work via open source initiatives. Thank you 🙏

© 2024 – Pkg Stats / Ryan Hefner

@woocommerce/expression-evaluation

v1.0.0

Published

Library for evaluating expressions.

Downloads

285

Readme

@woocommerce/expression-evaluation

Evaluation of JavaScript-like expressions in an optional context.

Examples of simple expressions:

1 + 2
foo === 'bar'
foo ? 'bar' : 'baz'

Examples of complex expressions:

foo.bar.baz === 'qux'
foo.bar
  && ( foo.bar.baz === 'qux' || foo.baz === 'quux' )
foo.bar
	&& ( foo.baz === "qux" || foo.baz === "quux" )
	&& ( foo.quux > 1 && foo.quux <= 5 )
foo.bar
	  && ( foo.baz === "qux" || foo.baz === "quux" )
	  && ( foo.quux > 1 && foo.quux <= 5 )
	? "boo"
	: "baa"
foo
  + 5
  /* This is a comment */
  * ( bar ? baz : qux )

API

evaluate

Evaluates an expression in an optional context.

Usage

import { evaluate } from '@woocommerce/expression-evaluation';

const result = evaluate( '1 + foo', { foo: 2 } );

console.log( result ); // 3

Parameters

  • expression string: The expression to evaluate.
  • context Object: Optional. The context to evaluate the expression in. Variables in the expression will be looked up in this object.

Returns

  • any: The result of the expression evaluation.

Expression syntax

Grammar and types

The expression syntax is based on JavaScript. The formal grammar is defined in parser.ts.

An expression consists of a single statement.

Features like if statements, for loops, function calls, and variable assignments, are not supported.

The following types are supported:

  • null
  • Boolean: true and false
  • Number: An integer or floating point number.
  • String: A sequence of characters that represent text.

Literals

Values in an expression can be written as literals.

null

null

Boolean

true
false

Number

1
5.23
-9

String

String literals can be written with single or double quotes. This can be helpful if the string contains a single or double quote.

'foo'
"foo"
'foo "bar"'
"foo 'bar'"

Quotes can be escaped with a backslash.

'foo \'bar\''
"foo \"bar\""

Context variables

Variables can be used in an expression. The value of a variable is looked up in the context.

const result = evaluate( 'foo', { foo: 1 } );

console.log( result ); // 1

Nested properties can be accessed with the dot operator.

const result = evaluate( 'foo.bar', { foo: { bar: 1 } } );

console.log( result ); // 1

Operators

The following operators are supported.

Comparison operators

Equal (==)

Returns true if the operands are equal.

1 == 1
Not equal (!=)

Returns true if the operands are not equal.

1 != 2
Strict equal (===)

Returns true if the operands are equal and of the same type.

1 === 1
Strict not equal (!==)

Returns true if the operands are not equal and/or not of the same type.

1 !== "1"
Greater than (>)

Returns true if the left operand is greater than the right operand.

2 > 1
Greater than or equal (>=)

Returns true if the left operand is greater than or equal to the right operand.

2 >= 2
Less than (<)

Returns true if the left operand is less than the right operand.

1 < 2
Less than or equal (<=)

Returns true if the left operand is less than or equal to the right operand.

2 <= 2

Arithmetic operators

Addition (+)

Returns the sum of two operands.

1 + 2
Subtraction (-)

Returns the difference of two operands.

2 - 1
Multiplication (*)

Returns the product of two operands.

2 * 3
Division (/)

Returns the quotient of two operands.

6 / 2
Modulus (%)

Returns the remainder of two operands.

5 % 2
Negation (-)

Returns the negation of an operand.

-1

Logical operators

Logical AND (&&)

Returns true if both operands are true.

true && true
Logical OR (||)

Returns true if either operand is true.

true || false
Logical NOT (!)

Returns true if the operand is false.

!false

Conditional (ternary) operator

Returns the first value if the condition is true, otherwise it returns the second value.

true ? 1 : 2

Comments

Comments can be used to document an expression. Comments are treated as whitespace and are ignored by the parser.

/* This is a comment */