Hướng dẫn javascript subtraction not working

I am trying to work on subtracting 2 values in Javascript. I had the addition working and then I just copied the code for subtraction [I just changed the operator]. But I am wondering why the subtraction is not working. Can you please tell me what did I miss?

Here's the code:

            function subNumbers[]
            {
                    var gross = parseFloat[document.getElementById["Gross"].value];
                    var tax   = parseFloat[document.getElementById["Tax"].value];
                    var other = parseFloat[document.getElementById["Other"].value];
                    var ded   = document.getElementById["TotalDed"];
                    ded.value = tax + other;
                    var net   = document.getElementById["Net"];
                    net.value = gross - ded;
            }
    

And then in the html part:

Thanks.

asked Feb 26, 2014 at 11:43

The problem is that:

Does not have an id attribute specified. Without id, document.getElementById['net']; fails.

Change it to:

And ded is an object, you need to use .value for both ded and net variables.

answered Feb 26, 2014 at 11:45

AashrayAashray

2,71515 silver badges22 bronze badges

0

becomes

and

net.value = gross - ded;

becomes

net.value = gross - ded.value;

answered Feb 26, 2014 at 11:47

// Assuming the following variable
//  bar = 5

bar -= 2     // 3
bar -= 'foo' // NaN

JavaScript Arithmetic Operators

Arithmetic operators perform arithmetic on numbers [literals or variables].

Arithmetic Operations

A typical arithmetic operation operates on two numbers.

The two numbers can be literals:

or variables:

or expressions:

Operators and Operands

The numbers [in an arithmetic operation] are called operands.

The operation [to be performed between the two operands] is defined by an operator.

Adding

The addition operator [+] adds numbers:

Subtracting

The subtraction operator [-] subtracts numbers.

Multiplying

The multiplication operator [*] multiplies numbers.

Dividing

The division operator [/] divides numbers.

Remainder

The modulus operator [%] returns the division remainder.

In arithmetic, the division of two integers produces a quotient and a remainder.

In mathematics, the result of a modulo operation is the remainder of an arithmetic division.

Incrementing

The increment operator [++] increments numbers.

Decrementing

The decrement operator [--] decrements numbers.

Exponentiation

The exponentiation operator [**] raises the first operand to the power of the second operand.

x ** y produces the same result as Math.pow[x,y]:

Operator Precedence

Operator precedence describes the order in which operations are performed in an arithmetic expression.

Is the result of example above the same as 150 * 3, or is it the same as 100 + 150?

Is the addition or the multiplication done first?

As in traditional school mathematics, the multiplication is done first.

Multiplication [*] and division [/] have higher precedence than addition [+] and subtraction [-].

And [as in school mathematics] the precedence can be changed by using parentheses:

When using parentheses, the operations inside the parentheses are computed first.

When many operations have the same precedence [like addition and subtraction], they are computed from left to right:

JavaScript Operator Precedence Values

Pale red entries indicates ECMAScript 2015 [ES6] or higher.

Expressions in parentheses are fully computed before the value is used in the rest of the expression.

Test Yourself With Exercises

Is there a

The subtraction assignment operator [ -= ] subtracts the value of the right operand from a variable and assigns the result to the variable.

How do you subtract in node JS?

subtract[] method is used to subtract the two date objects..

Required Module: Install the module by npm or used it locally. ... .

Syntax: const subtract[date1, date2].

Parameters: This method takes the following arguments as a parameter:.

Example 1: ... .

Output: total days between them 2270.3951833333335..

Example 2:.

How do you subtract two numbers in typescript?

Arithmetic Operators in Typescript.

+ [Addition].

– [Subtraction].

* [Multiplication].

/ [Division].

% [modulus or Reminder].

++ [Increment] & — [Decrement].

+ & – [Unary plus & Unary minus].

** [Exponentiation operator].