Javascript基础语法 - 良有以也

javascript数组从头部与尾部插入与删除
push pop shift unshift

javascript对象添加与删除属性
添加方法与修改一致，直接加上去即可
删除用delete ourDog.bark;

javascript是否拥有某个属性
hasOwnProperty

javascript随机数

Math.floor(Math.random() * (ourMax - ourMin + 1)) + ourMin;

正则表达式

/ is the start of the regular expression.

the is the pattern we want to match.

/ is the end of the regular expression.

g means global, which causes the pattern to return all matches in the string, not just the first one.

i means that we want to ignore the case (uppercase or lowercase) when searching for the pattern.

注意：\d表示数字，＼D表示相反

javascript数组变换
map reduce filter sort concat

var oldArray = [1, 2, 3];
var timesFour = oldArray.map(function(val){
  return val * 4;
});
console.log(timesFour); // returns [4, 8, 12]
console.log(oldArray);  // returns [1, 2, 3]


var singleVal = array.reduce(function(previousVal, currentVal) {
  return previousVal - currentVal;
}, 0);


var newArray = oldArray.filter(function(val){
  if(val<6){
    return val;
  }
});

sort can be passed a compare function as a callback. The compare function should return a negative number if a should be before b, a positive number if a should be after b, or 0 if they are equal.

var array = [1, 12, 21, 2];
array.sort(function(a, b) {
  return a - b;
});


var myArray = [1, 2, 3];
myArray.reverse();

同时还有string的split与join

javascript逆转字符串

function palindrome(str) {
  // Good luck!
  var re = /[^a-zA-Z0-9]/g;
  var t1=str.replace(re,"");
  var t2=t1.toLowerCase();
  var temStr=t2.split("").reverse().join("");
  if(temStr==t2){
  return true;
  }else{
  return false;
}
  
}
palindrome("eye");

javascript将首字母变为大写，其他变为小写

  function titleCase(str) {
  var tempStr=str.split(" ");
  var tempStr2=[];
  
  for(var i=0;i<tempStr.length;i++){
    var tempStr3=[];
    for(var j=0;j<tempStr[i].length;j++){
      if(j==0){
        tempStr3.push(tempStr[i][j].toUpperCase());
      }else{
        tempStr3.push(tempStr[i][j]); 
      }
      
    }
    tempStr2.push(tempStr3.join(""));
  }
  str=tempStr2.join(" ");
  //alert(str);
  return str;
}

javascript是否以某个字符串结尾

function confirmEnding(str, target) {
  // "Never give up and good luck will find you."
  // -- Falcor
  var n=target.length;
  var temp=str.substr(-n,n);
  if(temp==target){
    return true;
  }
  return false;
}

confirmEnding("Bastian", "n");

缩短字符串

function truncateString(str, num) {
  // Clear out that junk in your trunk
  if(num>=str.length){
    return str;
  }else{
    if(num<=3){
    var result=str.slice(0,num);
    return result+"...";
  }else{
    var result2=str.slice(0,num-3);
    return result2+"...";
  }  
  }
  
  
}

truncateString("A-tisket a-tasket A green and yellow basket", 11);

截取数组

slice截取到数组到后一个参数－1位

function slasher(arr, howMany) {
  // it doesn't always pay to be first
  var n=arr.length;
  if(howMany>=n){
    return [];
  }
  return arr.slice(howMany,n+1);
}

slasher([1, 2, 3], 2);

检测子串

function mutation(arr) {
  var first=arr[0];
  var second=arr[1];
  first=first.toLowerCase();
  second=second.toLowerCase();
  for(var i=0;i<second.length;i++){
    if(first.indexOf(second[i])==-1){
      return false;
    }else{
      
    }
  }
  return true;
}

mutation(["hello", "hey"]);

字符串rot编码

function rot13(str) { // LBH QVQ VG!
  var result="";
  for(var i=0;i<str.length;i++){
    if(str.charCodeAt(i)>=65&&str.charCodeAt(i)<78){
        
        result+=String.fromCharCode(str.charCodeAt(i)+26-13);  
    }else if(str.charCodeAt(i)>=78&&str.charCodeAt(i)<91){
      result+=String.fromCharCode(str.charCodeAt(i)-13); 
    }else{
      result+=str[i];
    }
    
  }
  return result;
}

// Change the inputs below to test
rot13("SERR PBQR PNZC");

使用jquery读取json数据

<script>
  $(document).ready(function() {

    $("#getMessage").on("click", function() {
      $.getJSON("/json/cats.json", function(json) {

        var html = "";

        json.forEach(function(val) {

          html += "<div class = 'cat'>";

          // Only change code below this line.
          html += "<img src = '" + val.imageLink + "' " + "alt='" + val.altText + "'>";
          
          
          // Only change code above this line.

          html += "</div>";

        });

        $(".message").html(html);

      });
    });
  });
</script>

<div class="container-fluid">
  <div class = "row text-center">
    <h2>Cat Photo Finder</h2>
  </div>
  <div class = "row text-center">
    <div class = "col-xs-12 well message">
      The message will go here
    </div>
  </div>
  <div class = "row text-center">
    <div class = "col-xs-12">
      <button id = "getMessage" class = "btn btn-primary">
        Get Message
      </button>
    </div>
  </div>
</div>

javascript获取你的经纬度

<script>
  // Only change code below this line.
  if (navigator.geolocation) {
  navigator.geolocation.getCurrentPosition(function(position) {
    $("#data").html("latitude: " + position.coords.latitude + "<br>longitude: " + position.coords.longitude);
  });
}
  
  
  // Only change code above this line.
</script>
<div id = "data">
  <h4>You are here:</h4>
  
</div>

javascript获取数组的最大值

var arr = [1, 2, 3];
var max = Math.max(...arr);