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hyoka uses a full recursive descent parser to parse expressions into AST, then evaluates to get the final result. it is very secure for math expressions unlike
by olamide203 4y ago
hyoka uses a full recursive descent parser to parse expressions into AST, then evaluates to get the final result. it is very secure for math expressions unlike the eval function which can run javascript code.
you can try out a demo here
https://codesandbox.io/s/naughty-chatterjee-kr3bsc https://codesandbox.io/s/naughty-chatterjee-kr3bsc
- gus_massa 4y agoNice! I was trying to change the expression, but I need to change it twice. At the top where `expression` is defined and at the bottom to show it in the html. Is it possible to "see" what is inside an Expression object?
- olamide203 4y agoyou can log it to the console if you want to see the Abstract syntax tree of an Expression object
- fuzzythinker 4y agoI would show examples in README on use of it along with string interpolation, as it's not too useful with only constants. Eg. const a = 3; const b = 2; const expression = new Expression(`${a}*${b}(6/3(5--2))`); const result = expression.evaluate(); document.getElementById("app").innerHTML = `a*b( 6 / 3( 5 - - 2 ) )= ${result}`; Edit: formating
- olamide203 4y agoNice tip, i'm planning to add an identifier node class so that you can pass a scope with the values to be used during evaluation. Eg. const a = 2; const b = 6; const c = 3 const expression = new Expression('a \ b * c') const result = expression.scope({a, b, c}).evaluate(); document.getElementById("app").innerHTML `${a} \ ${b} * ${c}= ${result}`
- gus_massa 4y ago[Add an empty line and then two spaces before each line to trigger the "code" mode.]
- fuzzythinker 4y agoVery welcome solution. String interpolation makes it possible, but it's bad DX.
- olamide203 4y agoyeah having to type ${} everywhere makes the code a little bit messy.