JS Review 1

1, the Regular:
/^[0-9a-zz-z_]*&///Match 0 to more, + is 1 to multiple,? 0 or more,. Any value
/^[0-9a-zz-z_]{6,}&///accurate to at least 6 bits
\w Finding Word characters
Test: Test ()
2, 1. One-time judgment: if () {} else{}
2. Multiple judgments: if () {}
if () {}
if () {}
if () {}
3. Grade Judgment:
var a=99;
var b=math.floor (A/10);
Console.log ("B:", B)
Switch (b) {
Case 9:console.log ("A"); Break
Case 8:console.log ("B"); Break
Case 7:console.log ("C"); Break
Case 6:console.log ("D"); Break
Default:console.log ("fail"); Break
}
3. Loop: (1) do {
}while ()
(2) while () {i++}//i++ in the loop body, the statement in the loop body affects i++
(3) The i++ in the for (i=0;i<=100;i++) {}//for is outside the loop body, and the statements in the loop body do not affect the i++
continue;//end this cycle, continue the next time
break;//jump out of the loop body

4, Bubble sort: n number, will compare n-1 wheel, each round less than the previous comparison

Bubble sort (multiple loops)
var arr1=[2,4,1,3,6,9,78,0];
for (Var i=0;i<arr1.length-1;i++) {
for (Var j=0;j<arr1.length-1-i;j++) {
if (Arr1[j]>arr1[j+1]) {
var tmp=arr1[j];
ARR1[J]=ARR1[J+1];
arr1[j+1]=tmp;
}

}

}
Console.log (ARR1);
5. Data type
(1) var obj={a:100};
var fun1=function (obj) {
obj.a++;
}
FUN1 (obj);//a=101 reference type
(2) a=100;
var fun1=function (a) {
a++;
}//Primitive Type
FUN1 ()//a=100
(3) var obj={a:100};
var fun1=function (obj) {
var obj={a:100};
obj.a++;
}
FUN1 (obj);//a=100
IsNaN () to determine if it is Nan
6. Operators
1. Arithmetic operator: +-*/%
2. Comparison operator:> < >= <= = = = = = =
3, 0==false;1==true;
2==true; (Error)
3, Var B;
if (b) {
}//b when there is a value
if (! b) {
}//b when there is no value

It is generally not recommended to write null and Undefi
4, A++,++a,a+=b,a-=b

6. Example
Bubble sort
var arr1=[2,4,1,3,6,9,78,0];
for (Var i=0;i<arr1.length-1;i++) {
for (Var j=0;j<arr1.length-1-i;j++) {
if (Arr1[j]>arr1[j+1]) {
var tmp=arr1[j];
ARR1[J]=ARR1[J+1];
arr1[j+1]=tmp;
}

}

}
Console.log (ARR1);
Arr1.foreach (function (value) {
Console.log (Value,i);
});

Var in method
For (var k in arr1) {
Console.log (K,arr1[k]);
}
var obj={
Name: "Zhang Fei",
Sex: "Male",
Age:16
}
For (var m in obj) {
Console.log ("Var in method", M,obj[m]);
}

foreach method
var arr2=[1,2,3,4,50];
var arr3=[];
Arr2.foreach (function (value) {
value=value*10;
Console.log (value);
Arr3.push (value);
})
Console.log (ARR3);

Map () Method 1, Do loop 2, in the loop can return the new array
var arr4=arr2.map (function (value) {
if (value>10)
{return value*10;}
else{
return value;
}
})
Console.log (ARR4);

Filter () Method: Do the filtering
var arr5=arr2.filter (function (value) {
if (value>10)
{return value;}
})
Console.log ("ARR5:", ARR5);

JS Review 1