Self assignment¶
ID: js/redundant-assignment
Kind: problem
Security severity:
Severity: warning
Precision: high
Tags:
- reliability
- correctness
- external/cwe/cwe-480
- external/cwe/cwe-561
Query suites:
- javascript-security-and-quality.qls
Click to see the query in the CodeQL repository
Assigning a variable to itself typically indicates a mistake such as a missing this qualifier or a misspelled variable name.
Recommendation¶
Carefully inspect the assignment to check for misspellings or missing qualifiers.
If the self-assignment is intentional and is needed for documentation or optimization purposes, add a JSDoc comment with a @type tag. This will indicate the self-assignment is intentional.
Example¶
In the example below, the constructor function Rectangle is intended to initialize properties x, y, width, and height to the parameters of the same names.
function Rectangle(x, y, width, height) {
this.x = x;
this.y = y;
width = width;
this.height = height;
}
Note, however, that on line 4 the programmer forgot to qualify the left hand side of the assignment with this: the code now performs a useless assignment of the width parameter to itself and leaves the width property uninitialized.
To fix this issue, insert a this qualifier:
function Rectangle(x, y, width, height) {
this.x = x;
this.y = y;
this.width = width;
this.height = height;
}