owncloud / gallery

Consider adding curly braces around all statements when they are executed conditionally. This is optional if there is only one statement, but leaving them out can lead to unexpected behaviour if another statement is added later.

Consider:

if (a > 0)
    b = 42;

If you or someone else later decides to put another statement in, only the first statement will be executed.

if (a > 0)
    console.log("a > 0");
    b = 42;

In this case the statement b = 42 will always be executed, while the logging statement will be executed conditionally.

if (a > 0) {
    console.log("a > 0");
    b = 42;
}

ensures that the proper code will be executed conditionally no matter how many statements are added or removed.

Consider adding curly braces around all statements when they are executed conditionally. This is optional if there is only one statement, but leaving them out can lead to unexpected behaviour if another statement is added later.

Consider:

if (a > 0)
    b = 42;

If you or someone else later decides to put another statement in, only the first statement will be executed.

if (a > 0)
    console.log("a > 0");
    b = 42;

In this case the statement b = 42 will always be executed, while the logging statement will be executed conditionally.

if (a > 0) {
    console.log("a > 0");
    b = 42;
}

ensures that the proper code will be executed conditionally no matter how many statements are added or removed.

The use of eval is discouraged because it can potentially make your code vulnerable to various injection attacks.

Besides it will also prevent certain optimizations that runtimes otherwise could make.

Consider adding curly braces around all statements when they are executed conditionally. This is optional if there is only one statement, but leaving them out can lead to unexpected behaviour if another statement is added later.

Consider:

if (a > 0)
    b = 42;

If you or someone else later decides to put another statement in, only the first statement will be executed.

if (a > 0)
    console.log("a > 0");
    b = 42;

In this case the statement b = 42 will always be executed, while the logging statement will be executed conditionally.

if (a > 0) {
    console.log("a > 0");
    b = 42;
}

ensures that the proper code will be executed conditionally no matter how many statements are added or removed.

Consider adding curly braces around all statements when they are executed conditionally. This is optional if there is only one statement, but leaving them out can lead to unexpected behaviour if another statement is added later.

Consider:

if (a > 0)
    b = 42;

If you or someone else later decides to put another statement in, only the first statement will be executed.

if (a > 0)
    console.log("a > 0");
    b = 42;

In this case the statement b = 42 will always be executed, while the logging statement will be executed conditionally.

if (a > 0) {
    console.log("a > 0");
    b = 42;
}

ensures that the proper code will be executed conditionally no matter how many statements are added or removed.

This checks looks for references to variables that have not been declared. This is most likey a typographical error or a variable has been renamed.

To learn more about declaring variables in Javascript, see the MDN.

Requirement of semicolons purely is a coding style issue since JavaScript has specific rules about semicolons which are followed by all browsers.

Further Readings:

• An Open Letter to JavaScript Leaders Regarding Semicolons by Isaac Schlueter
• JavaScript Semicolon Insertion

Consider adding curly braces around all statements when they are executed conditionally. This is optional if there is only one statement, but leaving them out can lead to unexpected behaviour if another statement is added later.

Consider:

if (a > 0)
    b = 42;

If you or someone else later decides to put another statement in, only the first statement will be executed.

if (a > 0)
    console.log("a > 0");
    b = 42;

In this case the statement b = 42 will always be executed, while the logging statement will be executed conditionally.

if (a > 0) {
    console.log("a > 0");
    b = 42;
}

ensures that the proper code will be executed conditionally no matter how many statements are added or removed.

Consider adding curly braces around all statements when they are executed conditionally. This is optional if there is only one statement, but leaving them out can lead to unexpected behaviour if another statement is added later.

Consider:

if (a > 0)
    b = 42;

If you or someone else later decides to put another statement in, only the first statement will be executed.

if (a > 0)
    console.log("a > 0");
    b = 42;

In this case the statement b = 42 will always be executed, while the logging statement will be executed conditionally.

if (a > 0) {
    console.log("a > 0");
    b = 42;
}

ensures that the proper code will be executed conditionally no matter how many statements are added or removed.

This check looks for variables that are declared in multiple lines. There may be several reasons for this.

In the simplest case the variable name was reused by mistake. This may lead to very hard to locate bugs.

If you want to reuse a variable for another purpose, consider declaring it at or near the top of your function and just assigning to it subsequently so it is always declared.

Consider adding curly braces around all statements when they are executed conditionally. This is optional if there is only one statement, but leaving them out can lead to unexpected behaviour if another statement is added later.

Consider:

if (a > 0)
    b = 42;

If you or someone else later decides to put another statement in, only the first statement will be executed.

if (a > 0)
    console.log("a > 0");
    b = 42;

In this case the statement b = 42 will always be executed, while the logging statement will be executed conditionally.

if (a > 0) {
    console.log("a > 0");
    b = 42;
}

ensures that the proper code will be executed conditionally no matter how many statements are added or removed.

Consider adding curly braces around all statements when they are executed conditionally. This is optional if there is only one statement, but leaving them out can lead to unexpected behaviour if another statement is added later.

Consider:

if (a > 0)
    b = 42;

If you or someone else later decides to put another statement in, only the first statement will be executed.

if (a > 0)
    console.log("a > 0");
    b = 42;

In this case the statement b = 42 will always be executed, while the logging statement will be executed conditionally.

if (a > 0) {
    console.log("a > 0");
    b = 42;
}

ensures that the proper code will be executed conditionally no matter how many statements are added or removed.

Consider adding curly braces around all statements when they are executed conditionally. This is optional if there is only one statement, but leaving them out can lead to unexpected behaviour if another statement is added later.

Consider:

if (a > 0)
    b = 42;

If you or someone else later decides to put another statement in, only the first statement will be executed.

if (a > 0)
    console.log("a > 0");
    b = 42;

In this case the statement b = 42 will always be executed, while the logging statement will be executed conditionally.

if (a > 0) {
    console.log("a > 0");
    b = 42;
}

ensures that the proper code will be executed conditionally no matter how many statements are added or removed.

Even if this assignment is intended here, we recommend to make this explicit in order to make your code more readable and your intention clear:

var x;
if (x = 0) { // Very likely a bug.
    var b = 1;
}

// Instead

var x;
if (x === 0) {
    var b = 1;
}

functon setHeight(node, height) {
    do {
        node.height = height;
    } while (node = node.parentNode);
}

// Instead you could use

function setHeight(node, height) {
    do {
        node.height = height;
    } while ((node = node.parentNode) !== null);
}

var i = 0, sum;
for (i < 10; i += 1) {
    sum += i;
}

// Instead

var i = 0, sum;
for (i = 0; i < 10; i += 1) {
    sum += i;
}

Requirement of semicolons purely is a coding style issue since JavaScript has specific rules about semicolons which are followed by all browsers.

Further Readings:

• An Open Letter to JavaScript Leaders Regarding Semicolons by Isaac Schlueter
• JavaScript Semicolon Insertion

Even if this assignment is intended here, we recommend to make this explicit in order to make your code more readable and your intention clear:

var x;
if (x = 0) { // Very likely a bug.
    var b = 1;
}

// Instead

var x;
if (x === 0) {
    var b = 1;
}

functon setHeight(node, height) {
    do {
        node.height = height;
    } while (node = node.parentNode);
}

// Instead you could use

function setHeight(node, height) {
    do {
        node.height = height;
    } while ((node = node.parentNode) !== null);
}

var i = 0, sum;
for (i < 10; i += 1) {
    sum += i;
}

// Instead

var i = 0, sum;
for (i = 0; i < 10; i += 1) {
    sum += i;
}

Requirement of semicolons purely is a coding style issue since JavaScript has specific rules about semicolons which are followed by all browsers.

Further Readings:

• An Open Letter to JavaScript Leaders Regarding Semicolons by Isaac Schlueter
• JavaScript Semicolon Insertion

This requirement purely is a coding style requirement and is not required to run on JavaScript engines:

new Date; // Bad
new Date(); // Good

This requirement purely is a coding style requirement and is not required to run on JavaScript engines:

new Date; // Bad
new Date(); // Good

Consider adding curly braces around all statements when they are executed conditionally. This is optional if there is only one statement, but leaving them out can lead to unexpected behaviour if another statement is added later.

Consider:

if (a > 0)
    b = 42;

If you or someone else later decides to put another statement in, only the first statement will be executed.

if (a > 0)
    console.log("a > 0");
    b = 42;

In this case the statement b = 42 will always be executed, while the logging statement will be executed conditionally.

if (a > 0) {
    console.log("a > 0");
    b = 42;
}

ensures that the proper code will be executed conditionally no matter how many statements are added or removed.

Requirement of semicolons purely is a coding style issue since JavaScript has specific rules about semicolons which are followed by all browsers.

Further Readings:

• An Open Letter to JavaScript Leaders Regarding Semicolons by Isaac Schlueter
• JavaScript Semicolon Insertion

Consider adding curly braces around all statements when they are executed conditionally. This is optional if there is only one statement, but leaving them out can lead to unexpected behaviour if another statement is added later.

Consider:

if (a > 0)
    b = 42;

If you or someone else later decides to put another statement in, only the first statement will be executed.

if (a > 0)
    console.log("a > 0");
    b = 42;

In this case the statement b = 42 will always be executed, while the logging statement will be executed conditionally.

if (a > 0) {
    console.log("a > 0");
    b = 42;
}

ensures that the proper code will be executed conditionally no matter how many statements are added or removed.

Requirement of semicolons purely is a coding style issue since JavaScript has specific rules about semicolons which are followed by all browsers.

Further Readings:

• An Open Letter to JavaScript Leaders Regarding Semicolons by Isaac Schlueter
• JavaScript Semicolon Insertion

Requirement of semicolons purely is a coding style issue since JavaScript has specific rules about semicolons which are followed by all browsers.

Further Readings:

• An Open Letter to JavaScript Leaders Regarding Semicolons by Isaac Schlueter
• JavaScript Semicolon Insertion

Requirement of semicolons purely is a coding style issue since JavaScript has specific rules about semicolons which are followed by all browsers.

Further Readings:

• An Open Letter to JavaScript Leaders Regarding Semicolons by Isaac Schlueter
• JavaScript Semicolon Insertion

If JSHint finds too many errors in a file, it aborts checking altogether because it suspects a configuration issue.

Further Reading:

• JSHint Configuration Reference
• Scrutinizer Configuration for JSHint

This error message can for example pop up if you forget to assign the result of a function call to a variable or pass it to another function:

function someFunction(x) {
    (x > 0) ? callFoo() : callBar();
}

// JSHint expects you to assign the result to a variable:
function someFunction(x) {
    var rs = (x > 0) ? callFoo() : callBar();
}

// If you do not use the result, you could also use if statements in the
// case above.
function someFunction(x) {
    if (x > 0) {
        callFoo();
    } else {
        callBar();
    }
}