Collection of 107 Javascript Frequently Tested Statements_Basic Knowledge

1. document.write( " "); Output statement
2. The comment in JS is //
3. The traditional HTML document order is: document- >html- >(head, body)
4. The DOM order 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 lowercase to uppercase js: document.getElementById( "output ").value =
document.getElementById( "input ").value.toUpperCase();
7. Value types in JS: String, Number, Boolean, Null, Object, Function
8. Convert character type to numeric type in JS: parseInt(), parseFloat()
9. Convert numbers in JS to character type: ( " " variable)
10. The length of string in JS is: (length)
11. Characters and characters in JS The connection number is used.
12. The comparison operators in JS are: == equal to, != not equal to, >, >=, <. <=
13. Use of declared variables in JS :var to make a statement
14. Decision 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 window window.open(), close one Window: window.close(), window itself: self
20. Status bar settings: window.status= "Character";
21. Pop-up prompt message: window.alert( "Character");
22. Pop up the 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 connector: =
28. Create a document element: document.createElement(), document.createTextNode()
29. Get the element method: document.getElementById()
30. Set the values ​​of all text members in the form Empty:
var form = window.document.forms[0]
for (var i = 0; i if (form.elements.type = = "text "){
form.elements.value = " ";
}
}
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 the radio button group is selected.
34. Drop-down list Box value: 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 the string to uppercase: string.toUpperCase(); Convert the string to lowercase: string.toLowerCase();
37. Return characters 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 the two numbers, Math.pow(value1,10) returns
the tenth power of value1, Math.round(value1) rounding function, Math.floor (Math.random()*(n
1)) returns a random number
41. Define date variable: var today = new Date();
42. Date function list: dateObj.getTime( ) Get the time, dateObj.getYear() gets the year, dateObj.getFullYear() gets the four-digit year, dateObj.getMonth() gets
to the month, dateObj.getDate() gets the day, dateObj.getDay() gets the date , dateObj.getHours() gets the hours, dateObj.getMinutes() gets
minutes, dateObj.getSeconds() gets the seconds, dateObj.setTime(value) sets the time, dateObj.setYear(val) sets the year, dateObj.setMonth ( val) sets
month, dateObj.setDate(val) sets day, dateObj.setDay(val) sets day of week, dateObj.setHours sets hours, dateObj.setMinutes(val) sets
minutes, dateObj.setSeconds( val )Set 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 in a hyperlink When calling a JS function, use: (javascript:) to start with the function name
48. This js will not be executed in old browsers: