函數(shù)三要素：功能杭攻、參數(shù)鞭缭、返回值
1.函數(shù)定義和調(diào)用
<script>
//1.定義函數(shù)
function getSum(m) {
var sum = 0;
for(var i = 0;i<= m;i++){
sum += i;
}
console.log(sum);//55
}
//2.調(diào)用函數(shù)
getSum(10);
</script>
2.函數(shù)返回值
<script>
function getSum(n,m) {
var sum = 0;
for(var i = n;i <= m;i++){
sum += i;
}
return sum;
}
console.log(getSum(1,2)); //3
</script>
3.函數(shù)應(yīng)用
3.1 計算m-n之間的和
<script>
var Sum1= 0 ;
//m,n是形參
function getSum1(m,n) {
for(var i = m;i<= n ;i++ ){
Sum1 +=i;
}
console.log(Sum1);
}
//實參
getSum1(1,2); //3
</script>
3.2 求圓的面積
<script>
function getArea(r) {
//過濾undefined null "" 0 NaN
r= r||0;
var PI = 3.14;
return PI *r *r;
}
console.log(getArea(4)); //50.24
</script>
3.3 求2個數(shù)中的最大值
<script>
function getMax(a,b) {
return a>b?a:b;
}
console.log( getMax(10,12)); //12
</script>
3.4 求3個數(shù)中的最大值
<script>
function getMax1(a,b,c) {
return (a>b?a:b)>c?(a>b?a:b):c;
}
console.log(getMax1(1,2,3)); //3
</script>
3.5 求數(shù)組中最大的值
<script>
function getMax1(a,b,c) {
return (a>b?a:b)>c?(a>b?a:b):c;
}
console.log(getMax1(1,2,3)); //3
</script>
3.6 求數(shù)組中最小的值
<script>
function getArrayMin(array) {
array = array || [];
var min = array[0];
for (var i = 1; i < array.length; i++) {
if (min > array[i]) {
min = array[i];
}
}
return min;
}
console.log(getArrayMin([1234,12,11,1,34])); //1
</script>
Snip20170818_1.png
3.7 翻轉(zhuǎn)數(shù)組,返回一個新的數(shù)組
<script>
function reverseArray(array) {
array = array ||[];
var newArrray = [];
for(var i = array.length -1;i >=0;i--){
newArrray[newArrray.length] = array[i];
}
return newArrray;
}
console.log(reverseArray([1,2,3,4,5]));
</script>
3.8 對數(shù)組排序,從小到大
<script>
//6.對數(shù)組排序,從小到大
function getSort(array) {
array = array ||[];
//a.外層循環(huán),控制趟數(shù)
for(var i = 0 ; i< array.length-1;i++){
var isSort = true;
//b.內(nèi)層循環(huán),控制比較次數(shù)
for(var j = 0; j<array.length-1-i;j++){
//c.判斷 比較大小,決定是否交換位置
if(array[j]>array[j+1]){
var temp = array[j];
array[j] = array[j+1];
array[j+1] =temp;
isSort = false;
}
}
//d.判斷是否已經(jīng)完成排序
if (isSort){
break;
}
}
//e.返回數(shù)組
return array;
}
console.log(getSort([123,456,78,76,5,43]));
</script>
Snip20170818_2.png
