66
77//TODO no works.
88
9- const firstElement = ( arr ) => {
10- const [ el ] = arr ;
11- return el ;
12- } ,
13- SECOND = 1 ;
9+ const
10+ firstElement = ( [ first ] ) => first ,
11+ secondElement = ( [
12+ , second
13+ ] ) => second ;
1414
1515module . exports = {
1616 meta : {
@@ -36,10 +36,15 @@ module.exports = {
3636 }
3737 } ) ;
3838 } ,
39- 'CallExpression[callee.type="MemberExpression"][callee.property.name="reduce"] > *:function > CallExpression[callee.type="MemberExpression"][callee.property.name="concat"]' ( node ) {
40- if ( node . parent . parent . arguments . length > SECOND && node . parent . parent . arguments [ SECOND ] . type === "ArrayExpression" &&
41- firstElement ( node . arguments ) . name === node . parent . params [ SECOND ] . name &&
42- node . callee . object . name === firstElement ( node . parent . params ) . name ) {
39+ 'CallExpression[callee.type="MemberExpression"][callee.property.name="reduce"][arguments.length=2][arguments.1.type=ArrayExpression][arguments.1.elements.length=0] > *:function[params.length=2][params.0.type=Identifier][params.1.type=Identifier] > CallExpression[callee.type="MemberExpression"][callee.property.name="concat"][arguments.length=1][arguments.0.type=Identifier]' ( node ) {
40+ const reduceCallbackParams = node . parent . params ;
41+ 42+ // arr.reducer((a, b) => a.concat(b), [])
43+ // "concat" function must be called on "a" and concat argument must be "b".
44+ if (
45+ firstElement ( node . arguments ) . name === secondElement ( reduceCallbackParams ) . name &&
46+ node . callee . object . name === firstElement ( reduceCallbackParams ) . name
47+ ) {
4348 context . report ( {
4449 node : node . parent . parent ,
4550 message : "Use flat to flatten an array" ,
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