JavaScript Syntax Basics

Number Type

JavaScript does not have an integer type and a float type. All numbers are treated as float by default.

 var total = 2 + 3;
 text = total; // this will convert the number to 5.0 

To force a number to be treated as an integer, use the toFixed() method of the number object and give a decimal point of zero:

 text = total.toFixed(0);
 // generates the string “5” 

A number constant is in decimal format by default, hexadecimal format if it starts with '0x', and octal format if it starts with '0'.

 decimal_number = 255 // -- Decimal is the default
 hex_number = 0xff
 fp_number = 2.456 // -- Floating point number 

Numerical computations are performed with the usual operators, +, *, /, -. The increment and decrement operators (++, --–) are also available.

String Type

You can designate String constants using single or double quotes:

 var mystring = "InetSoft Technology Corp." 
mystring = 'InetSoft Technology Corp.' 

Concatenate strings with the plus operator:

 var str = 'Total: ' + total; 

If a value concatenated to a string is of a different type, it is converted to a string automatically. Strings have many methods, for example, substring(), toLowerCase(), toUpperCase() and indexOf().

 var str = 'abcd';
str = str.toUpperCase(); // converts to ABCD 
var bIdx = str.indexOf('B'); //return 1 
str = str.substring(1, 2); // return 'b' 

Strings have built-in support for regular expressions. You can find a regular expression in a string using the match() or search() method:

 str = 'this is a test of regular expression';
re = /test/; // create a regular expression 
var idx = str.search(re); // return the position of the regular expression 

Arrays

An array is a list contained in a single variable. Each item in the list is known as an “element,” and the entire list is enclosed in square brackets ([]). When you create an array, it is initialized with the specified values as its elements. The following example creates the coffeelist array with three elements and a length of three:

var coffeelist = ["French Roast", "Columbian", "Kona"]; 

Multidimensional arrays are represented as an array of arrays. A two-dimensional array (rows and columns) may be created as follows:

var monthly_rain = [['Jan', 'Feb', 'Mar'],
[ 100,    10,   30  ],
[ 30,     10,   300 ],
[ 10,     10,   10  ]]; 

For Loop

A for loop instructs the server to repeat an action a specific number of times.

 //for (initial, condition-check, increment)
for (var j = 1; j < 10; j++) {
total = parseFloat(report['Table'].table[reg.y + j][3]); 
} 

The first expression in the loop (j = 1) initializes the loop variable. The second expression (j < 10) is a condition used to check when to terminate the loop (i.e., when the condition evaluates false). The third expression (j++) is the variable increment that is evaluated at the end of every iteration. The “j++” notation is the same as “j=j+1,” i.e., increment by one.

Switch Statement

The switch statement is similar to the if/else if/else structure. However, rather than choosing a branch to execute based on a binary condition, the Switch chooses a branch (i.e., a case) based on a value.

var day = CALC.weekdayname(CALC.today())
switch(day) {
case 'Sunday':
Text1.text = 'Note: ' + day + ' office closed.';
break;
case 'Thursday':
case 'Friday':
case 'Saturday':
Text1.text = 'Note: ' + day + ' hours are 10am-12pm.';
break;
default:
Text1.text = 'Note: ' + day + ' hours are 9am-5pm.'
break;
}

Note that one or more values can be listed on each case (e.g., Thursday, Friday, Saturday). A 'break' statement should be included at the end of each case to terminate the switch statement.

The “default” label at the end serves as the catch-all case. If the switch value does not match any of the explicit case values, then the “default” block is executed.