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JavaScript perguntas e respostas de entrevista

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Diferencas relacionadas

Pergunta 16. What type of variables are in Javascript?

Must declare variables before they’re used in the program
Declare at the top of the program & terminate each statement with ‘;’
Intialize variables when appropriate
Local variables (declared within a function) destroyed after function exit.
Can only be accessed within the function

Example – Note Assignments
var candyBarPrice = 2.50;
var taxRate = .075;
var candyBarsPurchased;

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Pergunta 17. What is Assignment Operator in Javascript?

Assignment ‘looks like’ equal sign but does NOT behave like it

subTotal = subTotal + 1.50

subTotal ‘is assigned the value’ that is currently in subTotal plus the value of 1.50

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Pergunta 18. What is Expression in Javascript?

An expression is a statement that describes a computation.
Usually look like algebra formulas
total = subTotal * taxRate
Operators (+, -, *, /, etc.) have different levels of precedence, similar to algebra
Don’t rely on it! For clarity, use parentheses.

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Pergunta 19. Explain String in Javascript?

Strings are sequences of keyboard characters enclosed in quotes
“Hello World” or ‘Hello World’

Variables can hold strings
var greeting = “Hello World”

String can be empty, i.e., contain no characters
var myAnswer = “”

Use ‘\’ (escape symbol) to ‘type’ prohibited characters
\b for backspace, \n for newline, \t for tab, \” for double quote.

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Pergunta 20. What is Date class in Javascript? Please explain.

to create a Date object, use new & supply year/month/day/… as desired

today = new Date(); // sets to current date & time

newYear = new Date(2002,0,1); //sets to Jan 1, 2002 12:00AM

methods include:

newYear.getYear() can access individual components of a date
newYear.getMonth()
newYear.getDay()
newYear.getHours()
newYear.getMinutes()
newYear.getSeconds()
newYear.getMilliseconds()

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