有人可以帮我弄清楚我的代码有什么问题吗？ 它将 RNA 序列翻译成蛋白质

Question

I have this code that translates RNA sequences into proteins. My question is where should I throw an error?. The code should throw an error after all tests have been checked. My problem is that if I throw the error at else if (rnaSequence[i] != key) throw new Error ('Invalid codon'); all other tests aren't evaluated.

...

let obj = {
  AUG: 'Methionine',
  UUU: 'Phenylalanine',
  UUC: 'Phenylalanine',
  UUA: 'Leucine',
  UUG: 'Leucine',
  UCU: 'Serine',
  UCC: 'Serine',
  UCA: 'Serine',
  UCG: 'Serine',
  UAU: 'Tyrosine',
  UAC: 'Tyrosine',
  UGU: 'Cysteine',
  UGC: 'Cysteine',
  UGG: 'Tryptophan',
  UAA: 'STOP',
  UAG: 'STOP',
  UGA: 'STOP'
}; 

const translate = (str) => {
  let rnaSequence = (str == null) ? null : str.match(/[A-Z]{1,3}/g);
  let proteinArr = [];

  for (let [key, value] of Object.entries(obj)) {
    if (rnaSequence == null) return proteinArr;
    else if (rnaSequence[0] == key) proteinArr.unshift(value);
    else for (let i = 1; i <= rnaSequence.length; i++) {
      if (rnaSequence[i] == key) proteinArr.push(value);
      // else if (rnaSequence[i] != key) throw new Error ('Invalid codon');
    }
  }

  for (let j = 0; j <= proteinArr.length; j++) {
    if (proteinArr[j] == "STOP") proteinArr.splice(j);
  }
  return proteinArr;
};
...


These are my tests:
...
 test('Small RNA strand', () => {
    expect(translate('AUGUUUUCU')).toEqual(['Methionine', 'Phenylalanine', 'Serine']);
  });

  xtest('Invalid codon throws error', () => {
    expect(() => translate('LOL')).toThrow(new Error('Invalid codon'));
  });

  xtest('Invalid codon throws error', () => {
    expect(() => translate('AUGOO')).toThrow(new Error('Invalid codon'));
  });

...

Answer 1

You're running this against every key in your object:

else if (rnaSequence[i] != key)

Let's say, for example, your RNA sequence is:

"AUGUUUUCU"

this is translated into the array:

["AUG", "UUU", "UCU"]

You then loop over every key-value pair in your object (ie the entries of your object). The first key being "AUG" . Your first if-condition is false, but the following if-condition will execute:

else if (rnaSequence[0] == key) proteinArr.unshift(value);

as rnaSequence[0] holds "AUG" and key also equals "AUG" . This now results in your RNA array looking like:

["Methionine", "AUG", "UCU", "UUU"]

as .unshift(value) will add the key's associated value to the array. You then proceed to your next key-value pair in your object. This time it is UUU: 'Phenylalanine' . Upon the second iteration, you again look at your if statements. The first if-condition is false , the second is also false , as "Methionine" is not equal to the key "UUU" . And so you're third if-condition would then be true, and so your error would be thrown.

---

If you want to fix your code you can create a results array. Instead of using unshift() on your RNA array, you can use .push() on the results array. You'd also need to loop over all keys in your object before you throw any errors to determine whether the RNA protein isn't in your object.

However, in my opinion, the easiest would be to re-think your approach. Currently, you're looping over your object to see if your RNA protein is in your object and to get its associated protein value. There are better ways to do this by using the key in obj or hasOwnProperty or simply indexing the object with bracket notation .

What I suggest to you is to get an array of RNA sequences from your original string like you are currently doing. Then, use .map() on this array to map each string to its associated protein by looking it up in the object:

"AUGUUUUCU" ---> ["AUG", "UUU", "UCU"] ---> ['Methionine', 'Phenylalanine', 'Serine']

You can also do some validation checks by using .every() to check that every RNA strand in your array has a key-value pair in the obj .

See example below:

 const obj = { AUG: 'Methionine', UUU: 'Phenylalanine', UUC: 'Phenylalanine', UUA: 'Leucine', UUG: 'Leucine', UCU: 'Serine', UCC: 'Serine', UCA: 'Serine', UCG: 'Serine', UAU: 'Tyrosine', UAC: 'Tyrosine', UGU: 'Cysteine', UGC: 'Cysteine', UGG: 'Tryptophan', UAA: 'STOP', UAG: 'STOP', UGA: 'STOP' }; const translate = str => { const rnaSequence = (str == null) ? null : str.match(/[AZ]{1,3}/g); if(!rnaSequence) return "Invalid codon"; // throw here instead: throw new Error ('Invalid codon'); const allValid = rnaSequence.every(key => key in obj); // check all keys in object if(!allValid) return "Invalid codon"; // throw here instead: throw new Error ('Invalid codon'); return rnaSequence.map(key => obj[key]); } console.log(translate('AUGUUUUCU')) // ['Methionine', 'Phenylalanine', 'Serine']); console.log(translate('LOL')) // new Error('Invalid codon') console.log(translate('AUGOO')) // new Error('Invalid codon')

Answer 2

You could either have a boolean variable that is set to true if an invalid sequence is hit (inside the else if) and then check that flag after the for loop within another if statement.

Or

You could have an array that gets invalid sequences pushed to it and then check if that array is empty or not after the for loop. This method is more descriptive if you're looking to see which ones failed.