CODEWITHSUNDEEP
javascriptjqueryregexvalidation
Pratheesh
Pratheesh

Reputation: 161

how to validate an expression based on certain requirement using javascript?

I have a numeric keypad it contains keys o to 9, an operator keypad with different operators like +,-,/,*,<,>,=,!=,<=,>=,== etc.

Next i have a list that contains the column names. The above requirement is to form an expression. When click the list of column names it put the value of column name in a text area box, then next selection is operator. If he want to add numeric items just click the item in numeric keypad.

My question is how can i validate the expression that the user entered in the text area is valid or not?

valid expression: ((mark1+mark2)/100)*100
valid expression:(mark1<=mark2)
invalid expression : ((mark1+5mark2)/100*100

(here a numeric value came along with column name 5mark2, also no closing bracket)

Upvotes: 1

Views: 86

Answers (2)

vusan
vusan

Reputation: 5331

Using instanceof and try catch

var isValid=0;
      var exp='(mark1+mark2)/100*100';
       try {
        eval(exp); 
        isValid=1;
       } 
catch(error){
    if (error instanceof TypeError) {

    } else if (error instanceof ReferenceError) {
        isValid=1;
    } else {

    }
}

Upvotes: 0

Obversity
Obversity

Reputation: 597

Just do the computation how you were planning to do it anyway, using a try-catch, and if it throws an error, you know that there's something wrong with it, so you can inform the user. You could do this in the background each time someone adds an item, perhaps.

Sounds easier than regex to me. Would that work?

Upvotes: 1

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