Exercises in Chapter 6 of Eloquent Javascript

Chapter6.js

// coming soon
// Ex. 6.1

function forEach(array, action) {
  for (var i = 0; i < array.length; i++)
    action(array[i]);
}

function reduce(combine, base, array) {
  forEach(array, function (element) {
    base = combine(base, element);
  });
  return base;
}

function addIfZero (base, element) {
    if (element == 0) {
	return (base + 1);
    }
    else
	return base;
}


//returns the number of zeroes in an array
function countZeros (array) {
    return reduce (addIfZero, 0, array);
}

function filterFN (test) {
    function addMe (base, element) {
	if (test (element))
	    return base + 1;
	else
	    return base;
    }
    return addMe;
}

function testIfZero (element) {
    return (element === 0); // no type coercion
}


function countIf (testFN, array) {
    var mycount = filterFN(testFN);
    return reduce (mycount, 0, array);
}

var myarr = [0,1,3,0,0];
countIf(testIfZero, myarr);
	
// okay, looking at the solutions, countIf could have been abstracted further 
// with a general equals function instead of just testing for 0

// Ex. 6.2

function isHeader (header) {
    // check for % and return the number of %
    for (var mychar in header) {
	if (header.charAt(mychar) != "%")
	    return Number(mychar);
    }
    return 0;
}

function processParagraph (paragraph) {
    // return an object with content: and type: properties
    var mypar = {content: paragraph, type: "p"}; // initialize with default
    var header = isHeader(paragraph);
    if (header > 0) {
	mypar.content = paragraph.slice(header);
	mypar.type = "h"+header;
    }
    return mypar;
}

var paragraphs = recluseFile().split("\n\n");
print("Found ", paragraphs.length, " paragraphs.");

function map(func, array) {
  var result = [];
  forEach(array, function (element) {
    result.push(func(element));
  });
  return result;
}

map (processParagraph, paragraphs);