How can I make multilevel object from string, which has structure like logic expression?

Question

As beginner, I don't know what is I can start from. I need to implement function which will transform string to object with particular structure like I wrote below (original string may be with other number of levels, conditionals etc.):

const str = `time !== 10 && (state === 'Ready' || state === 'Pending')`;

const result = {
  and: [
    {
      field: 'time',
      expression: '!==',
      value: 10
    },
    {
      or: [
        {
          field: 'state',
          expression: '===',
          value: 'Ready'
        },
        {
          field: 'state',
          expression: '===',
          value: 'Pending'
        }
      ]
    }
  ]
}

You want to create Abstract Syntax Tree (AST). Take a look on `github/esprima` for exmaple — captain-yossarian from Ukraine, Aug 03 '21 at 09:45
You say you're a beginner.. Sorry to say but seems like this is not a problem for a beginner to solve. Maybe start with something a little easier? :D — funkizer, Aug 03 '21 at 11:24
A great implementation of the Shunting Yard algorithm can be found at https://stackoverflow.com/questions/6479236/calculate-string-value-in-javascript-not-using-eval/47761792#47761792 — Trentium, Aug 03 '21 at 21:49

score 1 · Answer 1 · answered Aug 03 '21 at 12:14

The structure you mention is called an Abstract Syntax Tree (AST). This is a commom data structure that can represent the abstract structure of a word belonging to a language.

Your strings seem to be written in the infix order: you can try to implement the shunting yard algorithm to build the AST from the string.

As said in a comment, this is not a beginner problem. It would be better if you had some prior experience in data structures, algorithms, theory of languages/automata, and computer programming before implementing the shunting yard algorithm.

How can I make multilevel object from string, which has structure like logic expression?

1 Answers1