A, for circulation
The specified number of times execution code block
for (loop variable initialization; cycling conditions; loop variable change (increment or decrement)) {Code} loop
Steps:
1, loop condition is initialized (execution only when the first cycle time)
2, the loop condition is determined, the loop condition is true, step 3, the loop condition is false, then the loop ends
3, the body of code execution cycle
4, loop variable changes
5. The execution of the steps 2, 3, until the end of the loop
Examples: 1, 2, ...... 10 outputs the page
for(var i=0;i<10;i++){
document.write(i,<br>)
}
Or can be written as ( Declare variables can be put out for recycling, change the loop variable can be placed inside a for loop, however; must be retained )
var i = 0;
for( ; i<10 ; ){
document.write(i,<br>);
i++;
}
Note: 1, cycle condition changing + loop variable for controlling the number of times the loop body code execution
Second, double loop for
for(var j=0;j<3;j++){
for(var i=1;i<6;i++){
document.write(i,' ')
}
document.write('<br>')
}
1, the outer loop is executed for the first, outer loop variable is initialized, the loop condition, the code execution loop, encountered for the inner loop, the loop is finished for the inner, outer for-loop condition is determined to continue, the execution once the outer loop ......
Note: 1, each entry for the inner loop, the loop condition must initialize var i = 1
2, to perform an outer loop for, for the inner loop Once finished, only the outer loop for the next time
3, clearly distinguish between inner and outer loop of code for loop, in general, for the inner loop integral part of the cycle is for the outer loop of code
Third, the use of variables and string concatenation +
var str = 'hello'
str+'world' //helloworld
Third, create elements
DOM provides a range of ways to use JS to manipulate the DOM node (node creation page, access and other elements, adding elements)
1, create a node var newDiv = document.createElement ( 'span')
2, acquiring element node document.getElementById ( 'body') // assumed to body element id
3, the additive element node body.appenChild ( newDiv )
4, add the class name for the element
newDiv.className='active'