Summary of JavaScript basic knowledge and common methods

JAVASCRIPT is an indispensable part of AJAX technology, so if you want to learn AJAX and the popular AJAX framework well, learning JAVASCRIPT well is the most important.

1. Basic knowledge:

1.document.write(""); Output statement
2. The comment in JS is //
3. The traditional HTML document sequence is: document->html->(head,body)
4. The DOM sequence in a browser window is: window->(navigator, screen, history, location, document)
5. Get the name and value of the element in the form: document.getElementById("ID number of the element in the form").name (or value)
6. A JS that converts lowercase to uppercase: document.getElementById("output").value = document.getElementById("input").value.toUpperCase();
7. Value types in JS: String, Number, Boolean, Null, Object, Function
8. Convert character type in JS to numerical type: parseInt(), parseFloat()
9. Convert numbers in JS to character type: ("" variable)
10. The length of a string in JS is: (length)
11.Characters in JS are connected using the symbol.
12. The comparison operators in JS include: == equal to, != not equal to, >, >=, <.<=
13. To declare variables in JS, use: var to declare
14.Judgment statement structure in JS: if(condition){}else{}
15. Loop structure in JS: for([initial expression];[condition];[upadte expression]) {inside loop}
16. The command to terminate the loop is: break
17. Function definition in JS: function functionName([parameter],...){statement[s]}
18. When multiple forms appear in the file, you can use document.forms[0], document.forms[1] instead.
19. Window: open the window window.open(), close a window: window.close(), the window itself: self
20. Status bar settings: window.status="character";
21. Pop-up prompt message: window.alert("Character");
22. Pop up confirmation box: window.confirm();
23. Pop up the input prompt box: window.prompt();
24. Specify the location of the currently displayed link: window.location.href="URL"
25. Get the number of all forms in the form: document.forms.length
26. Close the output stream of the document: document.close();
27. String append concatenation: =
28. Create a document element: document.createElement(),document.createTextNode()
29. Method to get elements: document.getElementById()
30. Set the values of all text members in the form to be empty:

var form = window.document.forms[0]
for (var i = 0; i<form.elements.length;i++){
if (form.elements[i].type == "text"){
form.elements[i].value = "";
}
}

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31. Determine whether the check button is checked in JS: document.forms[0].checkThis.checked (the checked attribute represents whether it is selected and returns TRUE or FALSE)
32. Radio button group (the names of the radio buttons must be the same): take the length of the radio button group document.forms[0].groupName.length
33. Checked is also used to determine whether a radio button group is selected.
34. The value of the drop-down list box: document.forms[0].selectName.options[n].value (n sometimes uses the name of the drop-down list box plus .selectedIndex to determine the selected value)
35. Definition of string: var myString = new String("This is lightsword");
36. Convert a string to uppercase: string.toUpperCase(); Convert a string to lowercase: string.toLowerCase();
37. Return the position where string 2 appears in string 1: String1.indexOf("String2")!=-1 means it is not found.
38. Get a character at the specified position in the string: StringA.charAt(9);
39. Take out the substring with specified starting point and end point in the string: stringA.substring(2,6);
40. Mathematical functions: Math.PI (returns pi), Math.SQRT2 (returns square root), Math.max(value1, value2) returns the highest value of two numbers, Math.pow(value1,10) returns value1 to the tenth power, Math.round(value1) rounding function, Math.floor(Math.random()*(n 1)) returns a random number
41. Define date variables: var today = new Date();
42. List of date functions: dateObj.getTime() gets the time, dateObj.getYear() gets the year, dateObj.getFullYear() gets the four-digit year, dateObj.getMonth() gets the month, dateObj.getDate() gets the day, dateObj .getDay() gets the date, dateObj.getHours() gets the hours, dateObj.getMinutes() gets the minutes, dateObj.getSeconds() gets the seconds, dateObj.setTime(value) sets the time, dateObj.setYear(val) sets the year, dateObj.setMonth(val) sets the month, dateObj.setDate(val) sets the day, dateObj.setDay(val) sets the day of the week, dateObj.setHours sets the hours, dateObj.setMinutes(val) sets the minutes, dateObj.setSeconds(val) sets Seconds [Note: This date and time starts from 0]
43. FRAME representation: [window.]frames[n].ObjFuncVarName,frames["frameName"].ObjFuncVarName,frameName.ObjFuncVarName
44.parent represents the parent object, and top represents the top object
45. The parent window that opens the child window is: opener
46. Indicates the current location: this
47. When calling a JS function in a hyperlink, use: (javascript:) to start and add the function name
48. This JS is not executed in old browsers:
49. Quote a file-style JS:
50. Specify HTML to be displayed in browsers that do not support scripts:
51. When there are both hyperlinks and ONCLICK events, the old version of the browser will redirect to a.html, otherwise it will redirect to b.html. Example: dfsadf
52. The built-in objects of JS are: Array, Boolean, Date, Error, EvalError, Function, Math, Number, Object, RangeError, ReferenceError, RegExp, String, SyntaxError, TypeError, URIError
53. Line breaks in JS:/n
54. Window full screen size:

Summary of JavaScript basic knowledge and common methods_javascript skills