JavaScript Object Literals Syntax Error

JavaScript object literals syntax error

The NodeJS REPL evaluates code as an expression, by wrapping the code in parentheses, causing {"hello":1} to be ({"hello":1}) which is parsed successfully as an object literal.

Usually and elsewhere (in Chrome/Firefox's console), the curly braces are parsed as the delimiters of a block, like:

/*imagine if (true) */ {
    "hello": 1 // <-- What's this syntax? It's meaningless.
}

{hello:1} parses successfully, because hello in this context has the meaning of a label:

/*imagine if (true) */ {
    hello: 1;
} //        ^-- Automatic Semicolon Insertion

Why does this object literal cause a syntax error?

JavaScript object literals syntax error

Here is a similar answer (assuming you used the REPL). Basically Node will wrap the code in parentheses, thus parsing it successfully as an object literal.

{"hello":1} to be ({"hello":1})

javascript object literal dynamic key SyntaxError

You need to wrap your {} in (), or it will be interpreted as the body of a function:

['a', 'b'].map((x) => ({[x]: x }))

SyntaxError: Unexpected token ... in object literal

This code is using object spread properties, which are not a part of ECMAScript 6. They are currently an ECMAScript proposal at stage 3. To use them, you have to configure Babel to use stage-3 preset.

I can't write object literal notation in Dev Console?

{ /* ... */ } is a block statement.

If you want it to be parsed as an object initialiser, you must use it in a place where an expression is expected.

Some examples:

{} + ''; // `0`, parsed as block
'' + {}; // `"[object Object]"`, parsed as expression
{} * 1; // Error, parsed as block
1 * {}; // `NaN`, parsed as expression

A way to parse it as an expression and get the resulting object as the result is enclosing it inside parentheses:

({ /* ... */ })

Why does an object literal get ignored in a statement in JavaScript?

I would expect that if it was interpreted as a block, it would result in a syntax error. Why is this the case?

Inside a block, an expression consisting of a label followed by a number literal is valid.

but this does not answer how this is not a syntax error unless it is doing a lookahead to determine if it's an object literal or a block

It doesn't need to look ahead. It is a block because of what is on the left hand side of the { (i.e. nothing).

Javascript Object Syntax Error when declaring function

You're missing a comma in line 8, separating taxi.mileage and taxi.drive. You've also spelled 'function' incorrectly on line 9.

Fixing those, it seems to work fine:

var taxi = {    make: "Toyota",    model: "Taxi",    year: 1955,    colour: "yellow",    passengers: 4,    convertible: false,    mileage: 281341,    drive: function() {        alert("Voom Voom");    }};
function prequal(car) {    if (car.mileage > 10000 || car.year > 1960) {        return false;    }    return true;}
var worthALook = prequal(taxi);
if (worthALook) {    console.log("Check it out! " + taxi.make + " " + taxi.model);}else {    console.log("Not worth! " + taxi.make + " " + taxi.model);  }
taxi.drive();

JavaScript string literal in object literal syntax error

You have an unclosed string literal. JavaScript strings are not multi line by default.

var modalcontent = {
  description1 : '<div id = "description"><div class = "tbc"> '+
  '<label class = "tbc" for = "tbc">Description</label>'+
  '</div>'+
  '<div class = "tbc">'+
  '<input type = "text" class = "tbc" name = "description" id = "tbc" placeholder = "Enter description">'+
  '</div>'+
  '</div>'+
  '<!--end description div-->'
} 

(fiddle)

Alternatively, you can create multi line string by using the \ character, those only work in newer implementations. See this related question or the language specification.

Note: It's usually not the best idea to store HTML in strings, it makes it harder to debug and work with. You can usually use templates. It's not that there are no good use cases, it's just rarely the case.

Uncaught SyntaxError: Unexpected identifier in Object Literal

This is the correct syntax to assign a function to a property:

var myObject = {
    foo: 'bar',
    talk: function thisNameIsOptional() {
        console.log('Hello world')
    }
};

Also you can do it this way:

var myObject = {
    foo: 'bar',
    talk: talk
};

function talk() {
    console.log('Hello world')
}

As you see the syntax is always the same:

{
    literal1: (object or function),
    literal2: (object or function)

    ... and so on ...

}

The second one on your question is wrong.

If this is not enough, you have a complete guide for variables and literals on MDN.

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