I Can't See The Syntax Error!

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#1

Hi Everyone, I’ve been looking and looking at this and I’m no longer being productive. The code is throwing an syntax error on the line for (let percent = matchCount / 15 * 100) { saying:

SyntaxError: Unexpected token )

What am I not seeing?

      compareDNA(specimen) {
        let zip = [];
        let array1 = this.dna;
        let array2 = specimen.dna;
        let matchCount = 0
        for (let i = 0; i < array1.length; i++) {
          zip.push([array1[i], array2[i]]);
        } return zip;

       if (array1[i] === array2[i]) {
          matchCount++;
        }

        for (let percent = matchCount / 15 * 100) {
          percent.toFixed();
        } console.log('Specimen ' + this.specimenNum + ' and specimen ' + this.specimenNum ' have ' + percent + ' percent DNA in common.');
          }
        } 
      },


org1 = (pAequorFactory(1, mockUpStrand()));
org2 = (pAequorFactory(2, mockUpStrand()));
console.log(org1.compareDNA(org2));
#2

The syntax for a for loop is:

for (let i = 0; i < condition; i++) {
//code
}

You can change the variable names, condition, variable values, etc, but the basic template must be the same. Compare the above to yours:

for (let percent = matchCount / 15 * 100) {
    //code
}

Does it seem the same?

1 Like
#3

In addition to what @codeneutrino said, this return will stop your function all codes below it are unreachable.

2 Likes
#4

Thanks @codeneutrino ! I shouldn’t have used a for loop. I’ve changed it to an ordinary variable now.

1 Like
#5

Thank you @enghosamokasha ! I mistakenly left it in there after testing my code.

1 Like
#6

Thanks both for your help. I’ve amended the code but there’s still a syntax error thrown:

      compareDNA(specimen) {
        let zip = [];
        let array1 = this.dna;
        let array2 = specimen.dna;
        let matchCount = 0
        for (let i = 0; i < array1.length; i++) {
          zip.push([array1[i], array2[i]]);
        } 

       if (array1[i] === array2[i]) {
          matchCount++;
        }

        let percent = (matchCount / 15) * 100;
          percent.toFixed();
          console.log('Specimen ' + this.specimenNum + ' and specimen ' + this.specimenNum ' have ' + percent + ' percent DNA in common.');
          }
        } 
      },


org1 = (pAequorFactory(1, mockUpStrand()));
org2 = (pAequorFactory(2, mockUpStrand()));
console.log(org1.compareDNA(org2));
#7

What is the error? There seems to be a trailing } here (but it could just be the closing } of your function; I’d have to see the full code to know for sure):

let percent = (matchCount / 15) * 100;
          percent.toFixed();
          console.log('Specimen ' + this.specimenNum + ' and specimen ' + this.specimenNum ' have ' + percent + ' percent DNA in common.');
          }<----

and a trailing comma here:

let percent = (matchCount / 15) * 100;
          percent.toFixed();
          console.log('Specimen ' + this.specimenNum + ' and specimen ' + this.specimenNum ' have ' + percent + ' percent DNA in common.');
          }
        } 
      },<------
2 Likes
#8

I think you missed a + before ' have ', also may we see the full code?

what mockUpStrand() returns? and what is the reason for these extra parentheses?

1 Like
#9

Thank you so much all. I’ve edited my code with your suggestions. Still throwing errors though. Here is the full code:

// Returns a random DNA base
const returnRandBase = () => {
  const dnaBases = ['A', 'T', 'C', 'G']
  return dnaBases[Math.floor(Math.random() * 4)] 
}

// Returns a random single stand of DNA containing 15 bases
const mockUpStrand = () => {
  const newStrand = []
  for (let i = 0; i < 15; i++) {
    newStrand.push(returnRandBase())
  }
  return newStrand
}
 
const pAequorFactory = (specimenNum, dna) => {
    return {
      specimenNum : specimenNum,
      dna : dna,
      mutate() {
        let dnaM = this.dna[Math.floor(Math.random() * this.dna.length)];
        let randI = [Math.floor(Math.random() * 14)];
        this.dna.splice(randI, 1, dnaM);
        if (this.dna === mockUpStrand) {
          mutate()
        } else {
          return this.dna;
        }      
        },
      compareDNA(specimen) {
        let zip = [];
        let array1 = this.dna;
        let array2 = specimen.dna;
        let matchCount = 0
        for (let i = 0; i < array1.length; i++) {
          zip.push([array1[i], array2[i]]);
        } 
       if (array1[i] === array2[i]) {
          matchCount++;
        }

        let percent = (matchCount / 15) * 100;
          percent.toFixed();
          console.log('Specimen ' + this.specimenNum + ' and specimen ' + this.specimenNum + ' have ' + percent + ' percent DNA in common.');
          }
        } 
      },


org1 = (pAequorFactory(1, mockUpStrand()));
org2 = (pAequorFactory(2, mockUpStrand()));
console.log(org1.compareDNA(org2));

The error is now:

 if (array1[i] === array2[i]) {
              ^

ReferenceError: i is not defined

#10

The error occurs because you are using i in array1[i] and array2[i] outside its scope. just push this if inside the for loop.

for (let i = 0; i < array1.length; i++) {
          zip.push([array1[i], array2[i]]);
          if (array1[i] === array2[i]) {
              matchCount++;
          }
}

this will fix the error but, I’m not sure if this is the logic you want or not.

2 Likes
#11

I think you forgot to fix the error that @codeneutrino mentioned. you have an extra comma.

2 Likes
#12

Thank you! It’s not throwing any syntax errors now! It’s still not perfect but will work on it by myself for a while. Thanks again!

2 Likes
#13

keep going, And don’t worry we all make mistakes just relax and think, and also you can use a pen and a paper to analyze your code and thinking before coding :boom:.

2 Likes
#14

Thanks @enghosamokasha . It’s true! We learn through making mistakes so they are by no means a bad thing!

2 Likes