JavaScript Math Object and Built-in Functions: Fundamentals and Validation

1. INT222 – Internet Fundamentals Week 10: Math Object, Build-in Functions/Methods, JavaScript Validation

2. Outline • Math Object • Build-in Functions/Methods • JavaScript Validation • Assignment #3 released

3. JavaScript Math Object

4. Math functions (common method of the Math object) • Math.max(ident_1, ident_2) • the maximum of n numbers • e.g. alert( Math.max(0.52, 1) ); // 1 • Math.min(ident_1,ident_2) • the minimum of n numbers • e.g. alert( Math.min(0.52, 1) ); // 0.52 • Math.pow(ident_1, ident2) • ident_1 to the power ident_2 • e.g. alert( Math.pow(2, 8) ); // 256 • Math.sqrt(ident_1) • square root of • e.g. alert( Math. sqrt(9) ); // 3

5. Rounding floating-point • Math.ceil(ident_1) • integer closest to and not less than • e.g. alert( Math.ceil(0.52) ); // 1 alert( Math.ceil(0.49) ); // 1 • Math.floor(ident_1) • integer closest to and not greater than • e.g. alert( Math.floor(0.52) ); // 0 • Math.round(ident_1) • integer closest to • e.g. alert( Math.round(0.52) ); // 1 alert( Math.round(0.49) ); // 0 alert( Math.round(0.5) ); // 1

6. Generating Random Number • Math.random() - pseudorandom number • Return a floating point number between 0 (inclusive) and 1 (exclusive) • e.g. alert( Math.random() ); // 0.03517110995016992 • Generating number 1 to 10 Math.floor((Math.random()*10)+1);

7. JavaScriptBuilt-in Functions/Methods

8. escape(myString) function • Used to encode string, same as encodeURI() . • The function takes a non-alphanumeric string as its argument and returns the ASCII value (in hexadecimal form) for each character in the string preceded by a % sign. • If the string includes alphanumeric characters or -+*/_.@, those characters are returned unchanged. • Blank characters are returned as %20

9. Examples • alert( escape("qwertyuiopfghjklzxcvbnm") );// qwertyuiopfghjklzxcvbnm • alert( escape("QWERTYFGHJKLZXCVBNM") );// QWERTYFGHJKLZXCVBNM • alert( escape("1234567890-+*/_.@") );// 1234567890-+*/_.@ • alert( escape(" ~`!#$%^&()=\|\\[]{};':\",<>?") ); // %20%7E%60%21%23%24%25%5E%26%28%29%3D%7C%5C%5B%5D%7B%7D%3B%27%3A%22%2C%3C%3E%3F

10. eval(myString) function • The eval() function uses one argument: a string. • If the string is an expression, eval() evaluates/executes the expression. • If the string is made up of JavaScript statements, eval() performs the statements.

11. Example • var x = 10; • var y = 20; • var a = eval("x*y") + "\n"; • var b = eval("2+2") + "\n"; • var c = eval("x+17") + "\n"; • var res = a + b + c; • alert(res); Result: 200 4 27

12. isNaN(myString) function • The isNaN() function is used to determine if an argument is "NaN" (not a number). • example • alert( isNaN("123") ); // false • alert( isNaN(123) ); // false • alert( isNaN("123 456 789") ); // true • alert( isNaN("+123") ); // false • alert( isNaN("123+") ); // true • alert( isNaN(" 123 ") ); // false

13. parseFloat(myString) function • The parseFloat() function parses a string and returns a floating point number. • If a character other than a numeral, a sign (+ or -), or an exponent is found, the function returns the value up to that point. • If the first character in the string cannot be converted to a number, the function returns "NaN".

14. Example • alert( parseFloat("15.25") ); // 15.25 • alert( parseFloat("0.000345") ); // 0.000345 • alert( parseFloat("0.00159+E") ); // 0.00159 • alert( parseFloat(" 1234") ); // 1234 • alert( parseFloat("x 1234") ); // NaN • alert( parseFloat("1 2 3 4") ); // 1 • alert( parseFloat("1234 x 123") ); // 1234

15. parseInt(myString) function • The parseInt() function parses its first argument (a string), and then • tries to return an integer of the specified radix (or base).  • If a number in the string is beyond the base, parseInt() ignores the rest of the characters and returns an integer value up to that point.

16. Examples • base 10 (decimal) examples parseInt('15', 10) returns 15parseInt('15') returns 15parseInt(15.99, 10) returns 15parseInt('15*3', 10) returns 15parseInt('Hello') returns NaN • base 16 (hex) examples parseInt('F', 16) returns 15parseInt('FXX123', 16) returns 15

17. Examples • base 8 (octal) example parseInt('17', 8) returns 15parseInt('18', 8) returns 1 • base 2 (binary) example parseInt('1111', 2) returns 15parseInt('1211', 2) returns 1

18. Note the following problems parseInt('015',10) with base 10 returns 15 parseInt('015',8) with base 8 returns 13 parseInt('015',16) with base 16 returns 21 parseInt('15') with no base returns 15 - treated as decimal parseInt('015') with no base returns 15 - treated as octal parseInt('0x15') with no base returns 21 - treated as hex parseInt(' 15') with a blank returns 15

19. unescape(myString) function • The unescape() function is the exact opposite of the escape() function. Its argument is a string of ASCII values (in hexadecimal form), each preceded by a % sign. The function returns the character string. var myString1 = "%20%7E%60%21%23%24%25%5E%26%28%29%3D%7C%5C%5B%5D%7B%7D%3B%27%3A%22"; unescape(myString1) returns  ~`!@#$%^&()=|\[]{};':"

20. Number() function • The Number() function returns the actual number value - when possible var1 = truevar2 = false var3 = Mon Mar 17 2014 00:04:29 GMT-0400 (Eastern Daylight Time) Number(var1) = 1Number(var2) = 0 Number(var3) = 1395029069226 • var var1= new Boolean(true);var var2= new Boolean(false); • var var3= new Date();

21. Examples • varvar4= new String("999");var var5= new String("999 888");var var6= "999";var var7= "abc"; var4 = 999var5 = 999 888var6 = 999var7 = abc Number(var4) = 999Number(var5) = NaNNumber(var6) = 999Number(var7) = NaN

22. Parsing String to Number Without using functions varstr1 = "1234"; varnum1 = str1 * 1; alert(num1 + "\n" + typeof num1); varstr2 = "1234.5678"; varnum2 = +str2; alert(num2 + "\n" + typeof num2);

23. toFixed()Method • The toFixed() method formats a number to a specific number of digits to the right of the decimal. amount.toFixed() is : 165amount.toFixed(6) is : 165.254560amount.toFixed(2) is : 165.25 • var amount = 165.25456;

24. Popup window, getElementByIdand more • A demo:

25. Popup window syntax • Generate a popup window – on the fly : • Example: • HTML form button: • JS: getStarted() function in javascriptCode.js messageWindow=window.open('','window target name', 'window properties'); messageWindow.document.write(content); messageWindow.document.close(); <input type="button" name='example1' class='nice' value=' Popup and focus ' onclick="getStarted( );" />

26. Popup window syntax • Generate a popup window – Static : messageWindow=window.open('url','window target name', 'window properties'); messageWindow.document.close();

27. Get value of input field(type=text or similar) • Include • Input type: text, number, password, date, email, … • textarea • A values of input fields are strings, even if input type is number. • Example: HTML form and fields <form method='post' action=‘#' name='formexample'> … … <input type="text" name="example2" id="example2" size='35' class='inputtext' /> </form>

28. Get value of input field(type=text or similar) Three basic ways: • Check field value by Id • HTML: <a href="" onclick="return checkText2();">Check By Id</a><br /> • JavaScript checkText2() function in javascriptCode.js vartextLength = document.getElementById("example2").value.length; varactualText = document.getElementById("example2").value;

29. Get value of input field(type=text or similar) • Check field value by Document reference • HTML: <a href="" onclick="return checkText1();">Check Document reference</a> • JavaScript checkText1() function in javascriptCode.js vartextLength = document.formexample.example2.value.length; varactualText = document.formexample.example2.value;

30. Get value of input field(type=text or similar) • Check field value by object location • The index is based on • how many forms/elements in a page/form. • The sequence of the forms/elements in a page/form • HTML: <a href="" onclick="return checkText3();">Check By Ojbect Location</a> • JavaScript checkText3() function in javascriptCode.js vartextLength = document.forms[0].elements[2].value.length; varactualText = document.forms[0].elements[2].value;

31. Common sense logic • Checkbox fields <input type='checkbox' name='example4' value='1' onclick='commonSense();' />Option 1<br /> <input type='checkbox' name='example4' value='2' onclick='commonSense();' />Option 2<br /> <input type='checkbox' name='example4' value='3' onclick='commonSense();' />Option 3<br /> <input type='checkbox' name='example4' value='4' onclick='commonSense();' />Option 4<br /> <input type='checkbox' name='example4' value='any' onclick='uncheckTheAbove();' />Any of the above

32. Common sense logic • JavaScript Code function commonSense() { document.formexample.example4[document. formexample.example4.length - 1].checked = false; } function uncheckTheAbove() { varnumberOfCheckboxes2 = document.formexample.example4.length - 1; for (var j = 0; j < numberOfCheckboxes2 ; j++) { document.formexample.example4[j].checked = false; } }

33. JavaScript Validation

34. JS validation example of type="text" • By name • document.formname.elementname • By elementById • document.getElementById("elementid") method • By elementByName • document.getElementsByName("elementname") method • returns a collection • By form and element index • document.forms[index].elements[index] • Not recommended • With this key word • Using this key wordin form element

35. JavaScript validation - textarea example function checkForm() { vartextareaLength = document.example.comments.value.length; var messages="<p>No. of characters in textarea = <mark>" + textareaLength + "</mark></p>"; if (textareaLength==0) { messages+= "<p>You did not type any text in the textarea</p>"; showErrors(messages); return false; // return false - allow for changes - form not submitted } else { messages +="<p>You typed</p><p>" + document.example.comments.value + "</p>"; showErrors(messages); return false; // return true - form will be submitted } } // End of function … …

36. JS validation - type="checkbox" example • Checkbox logic • Get the number of the checkboxes using length • Loop to check which one was checked • To determine which one is checked - if any document.example.system_type[i].checked == true; // checked document.example.system_type[i].checked == false; // not checked

37. JS validation - type="radio" example • radio logic • Get the number of the radio using length • Loop to check which one was checked • To determine which one is checked - if any document.example.system_type[i].checked == true; // checked document.example.system_type[i].checked == false; // not checked

38. JavaScript validation - select examples • Select options logic • Get the selectedIndex: var x = document.example.whatToDo.selectedIndex; • If selectedIndex == -1 • None are selected • If the selectedIndex is NOT -1 • document.example.whatToDo.options[x].value; • for the value • document.example.whatToDo.options[x].text; • for the text

39. Text vs Value • For the <select> <option> elements – dropdown list <select> <option value=“This is a value">This is the text</option> <option value=" This is a value " selected> This is another text </option></select> • Any other form fields/controls have text attribute?

40. JavaScript validation - select / options - with multiple selections • Select options logic : **multiple="multiple" ** • Get the number of the select options using length document.example.whatToDo.options.length; • Loop to check which one was selected • To determine which one is selected • if any - check : if (document.example.whatToDo[i].selected == true) // selected • document.example.whatToDo[i].value • document.example.whatToDo[i].text

41. Thank You!