Exercise Solutions: Strings¶

Part One¶

1. Identify the result for each of the following statements:

1. 'JavaScript'[8] = 'p'

3. "Wonderful".length = 9

There's no code snippet for this one, just try it on your own with old-fashioned pen and paper!

2. The length method returns how many characters are in a string. However, the method will NOT give us the length of a number. If num = 1001, num.length returns undefined rather than 4.

1. Use type conversion to print the length (number of digits) of an integer.

let num = 1001;

3. What if num could be EITHER an integer or a decimal? Add an if/else statement so your code can handle both cases. (Hint: Consider the indexOf() or includes() string methods).

1if (String(num).includes('.')){
2console.log(String(num).length-1);
3} else {
4console.log(String(num).length);
5}

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Part Two¶

1. Remember, strings are immutable. Consider a string that represents a strand of DNA: dna = " TCG-TAC-gaC-TAC-CGT-CAG-ACT-TAa-CcA-GTC-cAt-AGA-GCT    ". There are some typos in the string that we would like to fix:

1. Use the trim() method to remove the leading and trailing whitespace, and then print the results.

1let dna = " TCG-TAC-gaC-TAC-CGT-CAG-ACT-TAa-CcA-GTC-cAt-AGA-GCT    ";
2let newString = dna.trim();
3console.log(newString);

3. Note that if you try console.log(dna) after applying the methods, the original, flawed string is displayed. To fix this, you need to reassign the changes back to dna. Apply these fixes to your code so that console.log(dna) prints the DNA strand in UPPERCASE with no whitespace.

1let dna = " TCG-TAC-gaC-TAC-CGT-CAG-ACT-TAa-CcA-GTC-cAt-AGA-GCT    ";
2dna = dna.trim().toUpperCase();
3console.log(dna);

1. Let's use string methods to do more work on the DNA strand:

1. Replace the sequence 'GCT' with 'AGG', and then print the altered Sstrand.

1dna = dna.replace('GCT','AGG');
2console.log(dna);

3. Use slice() to print out the fifth set of 3 characters (called a codon) from the DNA strand.

console.log(dna.slice(16,19));

5. Just for fun, apply methods to dna and use another template literal to print, 'taco cat'.

console.log(`${dna.slice(4,7).toLowerCase()}o ${dna.slice(dna.indexOf('CAT'),dna.indexOf('CAT')+3).toLowerCase()}`);

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Part Three¶

1. If we want to turn the string 'JavaScript' into 'JS', we might try .remove(). Unfortunately, there is no such method in JavaScript. However, we can use our cleverness to achieve the same result.

1. Use string concatenation and two slice() methods to print 'JS' from 'JavaScript'.

1let language = 'JavaScript';
2console.log(language.slice(0,1)+language.slice(4,5));

3. Use bracket notation and a template literal to print, "The abbreviation for 'JavaScript' is 'JS'."

console.log(`The abbreviation for '${language}' is '${initials}'.`)

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