Javascript Comparison Operators

5 Key excerpts on "Javascript Comparison Operators"

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  eBook - PDF

  JavaScript for Web Warriors

  • Patrick Carey, Sasha Vodnik, Patrick Carey(Authors)
  • 2021(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  When two numeric values are used as oper- ands, JavaScript interpreters compare them numerically. For example, the statement arithmeticValue = 5 > 4; results in true because the number 5 is numerically greater than the number 4. When two nonnumeric values are used as operands, the JavaScript interpreter compares them in lexicographical order—that is, the order in which they would appear in a dictionary. The expression "b" > "a"; returns true because the letter b comes after than the letter a in the Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. USING OPERATORS TO BUILD EXPRESSIONS 55 dictionary. When one operand is a number and the other is a string, JavaScript interpreters attempt to convert the string value to a number. If the string value cannot be converted to a number, a value of false is returned. For example, the expression 10 === "ten"; returns a value of false because JavaScript interpreters cannot convert the string “ten” to a number. Conditional Operators Comparison operators are often used with conditional operators or ternary operators that return one of two possible values given the Boolean value of comparison. The general syntax of a comparison operator is condition ? trueValue : falseValue; where condition is an expression or value that is either true or false, trueValue is the returned value if the expression is true, while falseValue is the returned value if the expression is false. The conditional expres- sion is often enclosed within parentheses to make the statement easier to read.

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  eBook - PDF

  JavaScript All-in-One For Dummies

  • Chris Minnick(Author)
  • 2023(Publication Date)
  • For Dummies

    (Publisher)

  Working with Operators and Expressions CHAPTER 4 Working with Operators and Expressions 85 x = (4-5-2) / (2*2); The result of this statement is -3 / 4, or -.75. Assignment operators The assignment operator assigns a value to the operand on the left based on the operand on the right: x = 10; You can also chain together assignment operators. For example: x = y = z = 0; Remember that the associativity of the assignment operator is from right to left. So, the way JavaScript executes this expression is by assigning 0 to z, and then the value of z to y, and then the value of y to x. In the end, all three variables are 0. Comparison operators The comparison operators test for equality of the left and right operands, and return a Boolean (true or false) value. Table 4-1 shows the complete list of com- parison operators. TABLE 4-1 Javascript Comparison Operators Operator Description Example == Equality 3 == “3” // true != Inequality 3 != 3 // false === Strict equality 3 === “3” // false !== Strict inequality 3 !== “3” // true > Greater than 7 > 1 // true >= Greater than or equal to 7 >= 7 // true < Less than 7 < 10 // true <= Less than or equal to 2 <= 2 // true 86 BOOK 1 JavaScript Fundamentals The equality and inequality operators (== and !=, respectively) only compare the values of the left and right operands. When possible, they change the type of the operand on the right to match the operand on the left. This behavior is, from the standpoint of JavaScript, a friendly thing to do. However, it results in some strange behaviors that can cause bugs in programs. For example, using the equality operator, the following statement evaluates to true: 0 == "0" In reality, the number 0 is not the same as a string containing a 0. Relying on JavaScript to automatically convert a string (for example, from a form input) to a number might not break your program, but it’s considered bad coding practice to use a string where you mean to use a number (or vice versa).

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  eBook - PDF

  Customizing Vendor Systems for Better User Experiences

  The Innovative Librarian's Guide

  • Matthew Reidsma(Author)
  • 2016(Publication Date)
  • Libraries Unlimited

    (Publisher)

  But in the case of strings, this will concatenate the strings for you. For instance: // Numeric variables var myVariable = 5; myVariable += 15; // Returns 20 // String variables var myVariable = "Today is "; myVariable += "Sunday"; // Returns "Today is Sunday" Comparison Operators Comparison operators are used to compare two values. These are useful when you need to compare two variables, or a variable to see if it has a value you’d expect, or whether it doesn’t have the value you expect it to have. These are the most common comparison operators: • == values are equal to each other • === values are equal and variables are of the same type • != values are not equal • < first value less than the second • > first value greater than the second • <= first value is less than or equal to the second • >= first value is greater than or equal to the second Later in this chapter, we’ll talk about conditionals, which allow us to run certain statements or functions only if certain conditions are met. We can test for those conditions using the comparison operators, like this: var myVariable = 5; if(myVariable > 2) { // Do something } 34 Customizing Vendor Systems for Better User Experiences METHODS AND PROPERTIES JavaScript includes a number of built-in methods that help you work with the contents of your variables. Some methods work with only one or two data types, so it’s good to know what kind of data type your variables are before you start planning to use methods. A full treatment of JavaScript methods is far beyond the scope of this chapter, but I will be using several string methods regularly in the examples that I’d like to introduce you to. In addition, the length property can be useful for both determining the length of strings and examining the number of values in an array.

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  No longer available |Learn more

  Professional JavaScript for Web Developers

  • Matt Frisbie(Author)
  • 2019(Publication Date)
  • Wrox

    (Publisher)

  false .

  The not identically equal operator is represented by an exclamation point followed by two equal signs (!== ) and returns true only if the operands are not equal without conversion. For example:

  let result1 = ("55" != 55); // false - equal because of conversion let result2 = ("55" !== 55); // true - not equal because different data types

  Here, the first comparison uses the not-equal operator, which converts the string "55" to the number 55, making it equal to the second operand, also the number 55. Therefore, this evaluates to false because the two are considered equal. The second comparison uses the not identically equal operator. It helps to think of this operation as saying, “Is the string 55 different from the number 55?” The answer to this is yes (true ).

  Keep in mind that while null == undefined is true because they are similar values, null === undefined is false because they are not the same type.

  NOTE   Because of the type conversion issues with the equal and not-equal operators, it is recommended to use identically equal and not identically equal instead. This helps to maintain data type integrity throughout your code.

  Conditional Operator

  The conditional operator is one of the most versatile in ECMAScript, and it takes on the same form as in Java, which is as follows:

  variable = boolean_expression ? true_value : false_value;

  This basically allows a conditional assignment to a variable depending on the evaluation of the boolean_expression . If it's true , then true_value is assigned to the variable; if it's false , then false_value is assigned to the variable, as in this instance:

  let max = (num1> num2) ? num1 : num2;

  In this example, max is to be assigned the number with the highest value. The expression states that if num1 is greater than num2 , then num1 is assigned to max . If, however, the expression is false (meaning that num1 is less than or equal to num2 ), then num2 is assigned to max

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  eBook - PDF

  Just Enough Programming Logic and Design

  • Joyce Farrell(Author)
  • 2012(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  Operator Name Discussion = Equivalency operator Evaluates as true when its operands are equivalent. Many languages use a double equal sign ( == ) to avoid confusion with the assignment operator. > Greater than operator Evaluates as true when the left operand is greater than the right operand. < Less than operator Evaluates as true when the left operand is less than the right operand. >= Greater than or equal to operator Evaluates as true when the left operand is greater than or equivalent to the right operand. When an operator is formed using two keystrokes, you never insert a space between them. <= Less than or equal to operator Evaluates as true when the left operand is less than or equivalent to the right operand. When an operator is formed using two keystrokes, you never insert a space between them. <> Not equal to operator Evaluates as true when its operands are not equivalent. Some languages use an exclamation point followed by an equal sign to indicate not equal to ( != ). When an operator is formed using two keystrokes, you never insert a space between them. Table 3-1 Relational comparison operators 70 C H A P T E R 3 Making Decisions Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Some programming languages allow you to compare a character to a number. If you do, then the character ’ s numeric code value is used in the comparison. For example, many computers use the American Standard Code for Information Interchange (ASCII) system or the Unicode system, in which an uppercase A is represented numerically as a 65, an uppercase B is a 66, and so on.

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