Converting JavaScript Array to CSV
var fruits = ['apple', 'peaches', 'oranges', 'mangoes'];
var str = fruits.join("|");
The valueOf() method will convert an array in javascript to a comma separated string.
Now what if you want to use pipe (|) as delimeter instead of comma. You can convert a js
array into a delimeted string using join() method
var fruits = ['apple', 'peaches', 'oranges', 'mangoes'];
var str = fruits.join("|");
Convert CSV to Array in JavaScript
var str = "apple,peaches,oranges,mangoes";
var fruitsArray = str.split(",");
Remove Array element by Index
function removeByIndex(arr, index) {
arr.splice(index, 1);
}
test = new Array();
test[0] = 'Apple';
test[1] = 'Ball';
test[2] = 'Cat';
test[3] = 'Dog';
alert("Array before removing elements: "+test);
removeByIndex(test, 2);
alert("Array after removing elements: "+test);
Remove Array element by Value
function removeByValue(arr, val) {
for(var i=0; i<arr.length; i++) {
if(arr[i] == val) {
arr.splice(i, 1);
break;
}
}
}
var somearray = ["mon", "tue", "wed", "thur"]
removeByValue(somearray, "tue");
Calling JavaScript function from String
var strFun = "someFunction"; //Name of the function to be called
var strParam = "this is the parameter"; //Parameters to be passed in function
//Create the function
var fn = window[strFun];
//Call the function
fn(strParam);
Generate Random number from 1 to N
//random number from 1 to N
var random = Math.floor(Math.random() * N + 1);
//random number from 1 to 10
var random = Math.floor(Math.random() * 10 + 1);
//random number from 1 to 100
var random = Math.floor(Math.random() * 100 + 1);
Deleting Multiple Values From Listbox in JavaScript
function selectBoxRemove(sourceID) {
//get the listbox object from id.
var src = document.getElementById(sourceID);
//iterate through each option of the listbox
for(var count= src.options.length-1; count >= 0; count--) {
//if the option is selected, delete the option
if(src.options[count].selected == true) {
try {
src.remove(count, null);
} catch(error) {
src.remove(count);
}
}
}
}
Listbox Select All/Deselect All using JavaScript
function listboxSelectDeselect(listID, isSelect) {
var listbox = document.getElementById(listID);
for(var count=0; count < listbox.options.length; count++) {
listbox.options[count].selected = isSelect;
}
}
Listbox Move selected items Up / Down
function listbox_move(listID, direction) {
var listbox = document.getElementById(listID);
var selIndex = listbox.selectedIndex;
if(-1 == selIndex) {
alert("Please select an option to move.");
return;
}
var increment = -1;
if(direction == 'up')
increment = -1;
else
increment = 1;
if((selIndex + increment) < 0 ||
(selIndex + increment) > (listbox.options.length-1)) {
return;
}
var selValue = listbox.options[selIndex].value;
var selText = listbox.options[selIndex].text;
listbox.options[selIndex].value = listbox.options[selIndex + increment].value
listbox.options[selIndex].text = listbox.options[selIndex + increment].text
listbox.options[selIndex + increment].value = selValue;
listbox.options[selIndex + increment].text = selText;
listbox.selectedIndex = selIndex + increment;
}
//..
//..
listbox_move('countryList', 'up'); //move up the selected option
listbox_move('countryList', 'down'); //move down the selected option
Listbox Move Left/Right Options
function listbox_moveacross(sourceID, destID) {
var src = document.getElementById(sourceID);
var dest = document.getElementById(destID);
for(var count=0; count < src.options.length; count++) {
if(src.options[count].selected == true) {
var option = src.options[count];
var newOption = document.createElement("option");
newOption.value = option.value;
newOption.text = option.text;
newOption.selected = true;
try {
dest.add(newOption, null); //Standard
src.remove(count, null);
}catch(error) {
dest.add(newOption); // IE only
src.remove(count);
}
count--;
}
}
}
//..
//..
listbox_moveacross('countryList', 'selectedCountryList');
Rounding Numbers to ‘N’ Decimals
var num = 2.443242342;
alert(num.toFixed(2)); // 2.44
// Note that we use toFixed() method here. toFixed(n) provides n length after the decimal point; whereas toPrecision(x) provides x total length::
num = 500.2349;
result = num.toPrecision(4); // result will equal 500.2
Remove Duplicates from JavaScript Array
function removeDuplicates(arr) {
var temp = {};
for (var i = 0; i < arr.length; i++)
temp[arr[i]] = true;
var r = [];
for (var k in temp)
r.push(k);
return r;
}
// Usage
var fruits = ['apple', 'orange', 'peach', 'apple', 'strawberry', 'orange'];
var uniquefruits = removeDuplicates(fruits);
// print uniquefruits ['apple', 'orange', 'peach', 'strawberry'];
Trim a String in JavaScript
if (!String.prototype.trim) {
String.prototype.trim=function() {
return this.replace(/^\s+|\s+$/g, '');
};
}
//usage
var str = " some string ";
str.trim();
//print str = "some string"
Redirect webpage in JavaScript
This javascript code should perform http redirect on a given URL
window.location.href = "http://viralpatel.net";
Encode a URL in JavaScript
var myOtherUrl = "http://example.com/index.html?url=" + encodeURIComponent(myUrl);
进一步阅读：21 JavaScript Tips And Tricks For JavaScript Developers
Equality
Strict equality checks (===) should be used in favor of ==. The only exception
is when checking for undefined and null by way of null.
// Check for both undefined and null values, for some important reason.
undefOrNull == null;
Type Checks
http://contribute.jquery.org/style-guide/js/
内部函数中的this
var name = "clever coder";
var person = {
name: "foocoder",
hello: function (sth) {
var sayhello = function (sth) {
console.log(this.name + " says " + sth);
};
sayhello(sth);
}
}
person.hello("hello world"); // clever coder says hello world
JavaScript的内部函数中，this没有按预想的绑定到外层函数对象上，而是绑定到了全局对象。
这里普遍被认为是JavaScript语言的设计错误，因为没有人想让内部函数中的this指向全局函数。
一般的处理方式是将this作为变量保存下来，一般约定为that或者self
var name = "clever coder";
var person = {
name: "foocoder",
hello: function (sth) {
var that = this;
var sayhello = function (sth) {
console.log(that.name + " says " + sth);
};
sayhello(sth);
}
}
person.hello("hello world"); // foocoder says hello world
名称解析顺序
JavaScript中的所有作用域，包括全局作用域，都有一个特别的名称 this 指向当前对象。
函数作用域内也有默认的变量 arguments ，其中包含了传递到函数中的参数。
比如，当访问函数内的 foo 变量时，JavaScript会按照下面顺序查找：
var foo 的定义。foo 名称的。foo 。