drills_solutions.md

Week 2 Drills -- solutions

isEmpty()

function isEmpty() {
  return !onBlue() && !onGreen();
}

moveRight(n)

function moveRight(n) {
  n = n || 1; // by default move 1 space if n is not defined
  for(var i=0; i<n; i++){
    $(".instructions").append("<div>moveRight</div>");
    if(kyrel.x < row.x - 1) {
      kyrel.x = kyrel.x + 1;
      updateRow();
    }
  }
}

moveLeft(n)

function moveLeft(n) {
  n = n || 1; // by default move 1 space if n is not defined
  for(var i=0; i<n; i++){
    $(".instructions").append("<div>moveLeft</div>");
    if(kyrel.x > 0) {
      kyrel.x = kyrel.x - 1;
      updateRow();
    }
  }
}

move(direction, times)

function move(direction, times) {
  if (direction === "r") {
    moveRight(times);
  } else if (direction === "l") {
    moveLeft(times);
  }
}

n_cell_rows

Hint: You will need to dynamically generate html and add it to the row in the DOM. Start by removing all the td elements from index.html. How would you add them back using javascript/jquery?

HTML Strings

Good:

function buildGithubLink(student) {
  var full_name = student.first_name + " " + student.last_name;
  var url = "http://github.com/" + student.github_username;
  return "<a href='" + url + "'>" + full_name + "</a>";
}

function renderGithubLinks(students){
  students.forEach(function(student){
    var link = buildGithubLink(student);
    $("body").append( link + "</br>" );
  });
}

renderGithubLinks( data.students );

Better optimized:

function renderGithubLinks(students){
  var anchors = students.map(buildGithubLink);
  var html = anchors.join("</br>");
  $("body").append( html );
}

renderGithubLinks( data.students );

Letter Frequency Counter

Good:

function characterFrequency(str){
  var output = {};

  str.split("").forEach(function(char){
    if ( char !== " " ) {
      var count = output[char];
      if ( count === undefined ) {
        output[char] = 1;
      } else {
        output[char] = count + 1;
      }
    }
  })

  return output;
}

Better:

function characterFrequency(str){
  var output = {},
      len = str.length,
      char,
      count;

  for(var i=0; i<len; i++) {
    char = str[i];
    if ( char === " " ) { continue; }
    count = output[char];
    output[char] = ( count ? count + 1 : 1 );
  }

  return output;
}

Merge

Pending