7.9. Exercises: Strings

7.9.1. Part One

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

    1. 'JavaScript'[8]
    2. "Strings are sequences of characters."[5]
    3. "Wonderful".length
    4. "Do spaces count?".length

    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.
    2. Print the number of digits in a DECIMAL value (e.g. num = 123.45 has 5 digits but a length of 6).
      1. Modify your code to print out the length of a decimal value EXCLUDING the period.
    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).

    Code it at repl.it

7.9.2. 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.
    2. Change all of the letters in the dna string to UPPERCASE and print the result.
    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.

    Code it at repl.it

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

    1. Replace the gene 'GCT' with 'AGG', and then print the altered strand.
    2. Look for the gene 'CAT' with indexOf(). If found print, 'CAT gene found', otherwise print, 'CAT gene NOT found'.
    3. Use slice() to print out the fifth gene (set of 3 characters) from the DNA strand.
    4. Use a template literal to print, "The DNA string is ___ characters long."
    5. Just for fun, apply methods to dna and use another template literal to print, 'taco cat'.

    Code it at repl.it

7.9.3. 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'.
    2. Without using slice(), use method chaining to accomplish the same thing.
    3. Use bracket notation and a template literal to print, "The abbreviation for 'JavaScript' is 'JS'."
    4. Just for fun, try chaining 3 or more methods together, and then print the result.

    Code it at repl.it

  2. Some programming languages (like Python) include a title() method to return a string with Every Word Capitalized (e.g. 'title case'.title() returns Title Case). JavaScript has no title() method, but that won't stop us! Use the string methods you know to print 'Title Case' from the string 'title case'.

    Code it at repl.it