Googlescript - Regex test null before error-CodePudding

I wrote a google script function with regex to retrieve information from a web page. I get 10 information per page with 10 different regex, but the problem is that when an information is not present I have an error for the corresponding regex. RegularExp "TypeError: Cannot read property '1' of null.

I tried to do a test to avoid this error but as soon as the regex pattern doesn't find anything, it returns this error. I can't test before the error.

Translated with www.DeepL.com/Translator (free version)

if (typeof(regExp.exec(html)[1]) === "null") {
var lastName = "error";
}else {
var lastName = regExp.exec(html)[1];
}

Do you know how to test before Regex error and indicate the value is false or empty ?

Thanks

CodePudding user response：

The value in your var html is null, and you are trying to access the null value which has no properties. This causes the error "TypeError: Cannot read property '1' of null".

To fix this, add an if statement where it will check if regExp.exec(html) has value then add your if-else statement.

Your code should look like this:

  if(regExp.exec(html){
    if (typeof(regExp.exec(html)[1]) === "null"){
    var lastName = "error";
    }else {
    var lastName = regExp.exec(html)[1];
    }
  }

CodePudding user response：

Thanks Nikko, i have modified a little your answer and it's ok for one formula. But, there is the same problem with multi formula on regExp2.

if(regExp1.exec(html)){
    if (typeof(regExp1.exec(html)[1]) === "null"){
    var lastName = "error";
    }else {
    var lastName = regExp1.exec(html)[1];
    }
  }

    if(regExp2.exec(html)){
    if (typeof(regExp2.exec(html)[1]) === "null"){
    var lastName = "error";
    }else {
    var lastName = regExp2.exec(html)[1];
    }
  }

    if(regExp3.exec(html)){
    if (typeof(regExp3.exec(html)[1]) === "null"){
    var lastName = "error";
    }else {
    var lastName = regExp3.exec(html)[1];
    }
  }

Finally i have use try/catch

try {
    var lastName7 = regExp7.exec(html)[1];
  }
  catch(err) {
    var lastName7 ="error";
  } 
  Logger.log(lastName7); 

  try {
    var lastName8 = regExp8.exec(html)[1];
  }
  catch(err) {
    var lastName8 ="error";
  } 
  Logger.log(lastName8); 

try {
    var lastName9 = regExp9.exec(html)[1];
  }
  catch(err) {
    var lastName9 ="error";
  } 
  Logger.log(lastName9);