js02-Common Flow control statements

1.if Statements

Syntax: if (condition) {

Execution when conditions are in existence　　

}else{

Conditions do not set up the implementation

}

Cases

var ji  =;         if (ji>=20) {            Console.log (' congratulate you, eat chicken success, good fortune ')        }else{            Console.log ( ' I'm sorry to keep working hard next time ')                    }

2.switch Statements

Syntax: switch (value) {

Case value 1:

EXECUTE statement

Break

Case Value:

EXECUTE statement

Break

}

<script type= "Text/javascript" >//switch ("better") represents the condition. Case represents a statement that executes after a condition is met        Switch("Better0") {             Case"Good": Console.log ("Great place to stay")                 Break;  Case"Better": Console.log ("Very good")                 Break;  Case"Best": Console.log ("Eat ducks.")                 Break; default: Console.log ("The real dishes to play")                 Break; }            </script>

3while and do While statements

While syntax:

while (condition) {
Execute code block
}

<script type= "Text/javascript" >//Whilex Cycle                //1. Initialize the loop variable 2. Determine the loop condition 3, update the loop variable        vari = 1;//1. Initialize the loop variable                 while(i<=9) {//2. Judging the cycle conditions//Console.log (i)I= i+1;//3, update the loop variable. Remember these three steps        }                //Practice                //output all multiples of 1-100 between 3        varj = 1;  while(j<=100){            if(j%3===0) {Console.log (j)} J++; }            </script>

Do While syntax

Note: The do side executes the code block after do once and then judges the while condition.

do{
Execute code block
} while (condition);

<script type= "Text/javascript" >        //WhileLoop trilogy        //1. Initialize the variable   2. Judging the cycle Condition   3. Update the loop variable        // whether the while condition is true or not, the code in do is run first, and then the while is judged.        var i = 5;          Do {            Console.log (i)            i++        ;  while (i<10);     </script>

4 for statement

Grammar:

for (Var 1=10 initializes the variable, i>=1 is the condition, i--is the update variable. Use between each statement; separate)
for (var i = ten; i>=1; i--) {
Console.log (i)
}

<script type= "Text/javascript" >//For (var 1=10 initializes the variable, i>=1 is the condition, i--is the update variable. Use between each statement; separate)         for(vari = 10; i>=1; i--) {Console.log (i)}//even number of outputs 1-100         for(vari = 1; I <= 100; i++) {            if(i%2==0) {Console.log (i)}}//calculate between 1-100 and        //var sum=0        //For (var i = 1; i <=; i++) {        //sum+=i        //}console.log (sum)        //For (var i = 1; I <=3; i++) {        //For (var x =1; <=6; x + +) {        //document.write ("*")                        //}document.write ("<br>")                    // }</script>

array:

<script type= "Text/javascript" >/*How data is created: 1. Literal way 2. Function Construction Method*/        //The literal way, recommended this way. Because it's simple and straightforward.        varColors =["Red", "green", "blue"]; Console.log (colors)//using the constructor new        varColors2 =NewArray ("Balck", "white", "origin"); Console.log (COLORS2)//Array Assignment        varARR1 = []; arr1[0] = "www.google.com"; arr1[1] = "wwww.it.com"; arr1[2] = "www.sohu.com"; arr1[3] = "www.sina.com"; arr1[4] = "www.163.com"; //Console.log (arr1)         for(vari = 0; I <arr1.length; i++) {Console.log (arr1[i])}</script>

<script type= "Text/javascript" >//merging concat of arrays        //var North =["Henan", "Beijing", "Hebei";        //var South =["Shanghai", "Suzhou", "Hangzhou";        //var newArr = North.concat (south);        //Console.log (NEWARR)        //Convert to String toString () directly to string, separated by commas        varscore=[100,33,56,67,87]; varstr =score.tostring (); Console.log (str)//Join () method, using the specified string to split the array        varSTR2 = Score.join ("|"); Console.log (STR2)//indexOf () checks the subscript of a specified string, referring to a forward lookup        varindex = Score.indexof (67); varIndex1 = Score.indexof (99);//the lookup is not in the array, returns-1Console.log (Index) console.log (INDEX1)//lastindexOf (), flashback lookup. Note the index values for forward and reverse lookups are the same.        varIndex2 =score.lastindexof (67); Console.log (INDEX2)//Array of arrays to be sorted, and the original array will be reversed        varNames =["Alne", "Jack", "Chen", "Wang", "Liu", "Ago"]; varReversename =Names.reverse (); Console.log (Reversename) console.log (names)//in alphabetical order, if the first character is the same, in the following letter, and so on        varNames1 =Names.sort (); Console.log (names1)//removes the first element.        varFrist =Names.shift (); Console.log (frist) Console.log (names)//Unshift () adds one or more values and returns the length of the array.        varNames2 = Names.unshift ("Pinjin", "Xuehua", "Xiaohei"); Console.log (names) Console.log (names2)//push (), pop () Add, delete        //push () is added by default to the end of the array        varNames3 = Names.push ("Lirui", "Xiaoxiao"); Console.log (names) Console.log (NAMES3)//returns the new length        //pop () Delete defaults from the last start Delete, names4 is the deleted element        varNames4 =Names.pop ();        Names.pop ();        Names.pop (); Console.log (NAMES4)//split, invert string "Hello Luffy"        varA = "Hello Luffy"; //var x = A.split ("")Console.log (A.split (""). Reverse ())</script>

common methods for arraysfunction:

<script type= "Text/javascript" >//JS in the function is declared to be with function funcname (), there are functions of the Declaration, there must be a call.        functionAdd () {alert ("The function is called.")} Add ()//declaring a function with formal parameters        functionadd2 (x, y) {alert+y)} add2 (4,7)        //function with return value        functionAdd3 (A, b) {returnA *B}//Console.log (ADD3 (5,9))Alert (ADD3 (5,10))    </script>

js02-Common Flow control statements