edge-parser

Edge Parser

This repo is the parser to convert edge templates inside a self invoked Javascript function. Later you can invoke this function by providing a context.

Example:

Input

Hello {{ username }}

Output

(function (ctx) {
  let out = ''
  out += 'Hello '
  out += `${ctx.escape(ctx.resolve('username'))}`
  out += '\n'
  return out
})(ctx)

Notice of use of ctx in the function body. Parser doesn't provide the implementation of ctx, the runtime of template engine should provide it.

Supported Expressions

The following expressions are supported by the parser.

Identifier

The identifier is wrapped inside ctx.resolve. The resolve method job is to resolve the value.

In following statement username is the identifier

Hello {{ username }}

Literal

A string literal

Hello {{ 'Guest' }}

ArrayExpression

The [1, 2, 3, 4] is an array expression.

Evens are {{
  [1, 2, 3, 4].filter((num) => num % 2 === 0)
}}

ObjectExpression

The { username: 'virk' } is an Object expression

{{ toJSON({ username: 'virk' })  }}

UnaryExpression

Following are examples of UnaryExpression.

{{ typeof(username) }}

{{ !!username }} 

BinaryExpression

Here {{ 2 + 2 }} is the binary expression

{{ 2 + 2 }} = 4

LogicalExpression

Following is the example of LogicalExpression.

{{ username || admin.username }}

MemberExpression

{{ username.toUpperCase() }}

ConditionalExpression

{{ username ? username : 'Guest' }}

CallExpression

{{ upper(username) }}

SequenceExpression

Sequence is not supported in mustache blocks and instead used inside tags. For example:

Everything inside () is a sequence expression.

@component('button', text = 'Submit', type = 'Primary')

TemplateLiteral

{{ Hello `${username}` }}

ArrowFunctionExpression

{{
  users.map((user) => {
    return user.username
  })
}}

Context expectations

Context must have following methods to work with the core parser.

class Context {
  // Resolve value for a key
  resolve(key: string): any
  
  // make input HTML safe
  escape (input: string): string
}

Changelog

1.0.0 (2018-05-31)

Bug Fixes

• buffer: append new line with writeLine statement (d4852f5)
• parser: export must use es6 export syntax (b6a1e61)
• parser: wrap mustache nodes inside escape call (432cfed)

Features

• cover all allowed expression (5a415d8)
• initial commit (971bbd9)
• buffer: add writeStatement method (be705fd)
• buffer: expose edge buffer interface (b01d34b)
• errors: patch lineno in errors (ca7e93f)
• parser: handle block tokens too (08a4ded)
• parser: parse eacaped and safe mustache tokens (2dafb5e)