CODEWITHSUNDEEP
javascriptregexparsingpegjs
Benk I
Benk I

Reputation: 199

Parse expression with JavaScript using PEG.js

I have written the code to parse the following expression

=name1 OR <=name2

to

{
    operator: 'or',
    values: [
        {
            op: '=',
            value: 'name1 ',
        },
        {
            op: '<=',
            value: 'name2',
        },
    ],
}

using PEG.js. Please check the code sandbox.

But I am not getting how to parse the follwong expression

=name1 OR =name2 OR =name3 OR =name4

It should return the following structured object

{
    operator: 'or',
    values: [
        {
            op: '=',
            value: 'name1',
        },
        {
            op: '=',
            value: 'name2',
        },
        {
            op: '=',
            value: 'name3',
        },
        {
            op: '=',
            value: 'name4',
        }
    ],
}

code sandbox:https://codesandbox.io/s/javascript-testing-sandbox-forked-76n0p?file=/src/index.js

Upvotes: 1

Views: 164

Answers (1)

georg
georg

Reputation: 215059

I guess you can describe your language with the following grammar:

Expression = head:Term tail:(_ "OR" _ Term _)*  {
    return [head].concat(tail.map(t => t[3]))
}

Term = _ op:Operator _ name:Name  {
    return {op, name}
}

Operator = "=" / "=<"

Name = head:[a-z] tail:([a-z0-9]*) {
    return head + tail.join('')
}

_ = [ \t\n\r]*

You can try it online on https://pegjs.org/online

Upvotes: 2

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