ESLintenforce the location of single-line statements (nonblock-statement-body-position)
The --fix option on the command line can automatically fix some of the problems reported by this rule.
When writing if, else, while, do-while, and for statements, the body can be a single statement instead of a block. It can be useful to enforce a consistent location for these single statements.
For example, some developers avoid writing code like this:
if (foo)
bar();
If another developer attempts to add baz(); to the if statement, they might mistakenly change the code to
if (foo)
bar();
baz(); // this line is not in the `if` statement!
To avoid this issue, one might require all single-line if statements to appear directly after the conditional, without a linebreak:
if (foo) bar();
Rule Details
This rule aims to enforce a consistent location for single-line statements.
Note that this rule does not enforce the usage of single-line statements in general. If you would like to disallow single-line statements, use the curly rule instead.
Options
This rule accepts a string option:
"beside"(default) disallows a newline before a single-line statement."below"requires a newline before a single-line statement."any"does not enforce the position of a single-line statement.
Additionally, the rule accepts an optional object option with an "overrides" key. This can be used to specify a location for particular statements that override the default. For example:
"beside", { "overrides": { "while": "below" } }requires all single-line statements to appear on the same line as their parent, unless the parent is awhilestatement, in which case the single-line statement must not be on the same line."below", { "overrides": { "do": "any" } }disallows all single-line statements from appearing on the same line as their parent, unless the parent is ado-whilestatement, in which case the position of the single-line statement is not enforced.
Examples of incorrect code for this rule with the default "beside" option:
/* eslint nonblock-statement-body-position: ["error", "beside"] */
if (foo)
bar();
else
baz();
while (foo)
bar();
for (let i = 1; i < foo; i++)
bar();
do
bar();
while (foo)
Examples of correct code for this rule with the default "beside" option:
/* eslint nonblock-statement-body-position: ["error", "beside"] */
if (foo) bar();
else baz();
while (foo) bar();
for (let i = 1; i < foo; i++) bar();
do bar(); while (foo)
if (foo) { // block statements are always allowed with this rule
bar();
} else {
baz();
}
Examples of incorrect code for this rule with the "below" option:
/* eslint nonblock-statement-body-position: ["error", "below"] */
if (foo) bar();
else baz();
while (foo) bar();
for (let i = 1; i < foo; i++) bar();
do bar(); while (foo)
Examples of correct code for this rule with the "below" option:
/* eslint nonblock-statement-body-position: ["error", "below"] */
if (foo)
bar();
else
baz();
while (foo)
bar();
for (let i = 1; i < foo; i++)
bar();
do
bar();
while (foo)
if (foo) {
// Although the second `if` statement is on the same line as the `else`, this is a very common
// pattern, so it's not checked by this rule.
} else if (bar) {
}
Examples of incorrect code for this rule with the "beside", { "overrides": { "while": "below" } } rule:
/* eslint nonblock-statement-body-position: ["error", "beside", { "overrides": { "while": "below" } }] */
if (foo)
bar();
while (foo) bar();
Examples of correct code for this rule with the "beside", { "overrides": { "while": "below" } } rule:
/* eslint nonblock-statement-body-position: ["error", "beside", { "overrides": { "while": "below" } }] */
if (foo) bar();
while (foo)
bar();
When Not To Use It
If you’re not concerned about consistent locations of single-line statements, you should not turn on this rule. You can also disable this rule if you’re using the "all" option for the curly rule, because this will disallow single-line statements entirely.
Further Reading
Version
This rule was introduced in ESLint 3.17.0.