feat: handle invalid JSON lines

README.md

@@ -36,3 +36,8 @@ expect(result).to.deep.equal([
   { foo2: 'bar2' },
 ]);
 ```
+
+## specification
+* It omits every line which isn't a valid JSON.
+* For the remaining lines, it converts every line into an object.
+* So it always returns an array (possibly an empty array if there's no line with a valid JSON).

src/readJsonLines.js

@@ -1,7 +1,14 @@
 function readJsonLines(string) {
   return string.split('\n')
-    .filter(line => line)
-    .map(line => line.trim())
+    .filter((line) => {
+      try {
+        JSON.parse(line);
+
+        return true;
+      } catch (error) {
+        return false;
+      }
+    })
     .map(line => JSON.parse(line));
 }
 

src/tests/readJsonLines.js

@@ -66,4 +66,69 @@ describe('readJsonLines', () => {
       { foo3: 'bar3', lorem: [1, 2, 3] },
     ]);
   });
+
+  it('returns empty array for one invalid JSON line', () => {
+    const lines = 'foo';
+
+    const result = readJsonLines(lines);
+
+    expect(result).to.deep.equal([]);
+  });
+
+  it('returns empty array for two invalid JSON lines', () => {
+    const lines = `foo
+bar`;
+
+    const result = readJsonLines(lines);
+
+    expect(result).to.deep.equal([]);
+  });
+
+  it('returns a one-element array for a one-line string followed by one invalid JSON line', () => {
+    const lines = `{"foo":"bar"}
+baz`;
+
+    const result = readJsonLines(lines);
+
+    expect(result).to.deep.equal([
+      { foo: 'bar' },
+    ]);
+  });
+
+  it('returns a one-element array for a one-line string preceded by one invalid JSON line', () => {
+    const lines = `baz
+{"foo":"bar"}`;
+
+    const result = readJsonLines(lines);
+
+    expect(result).to.deep.equal([
+      { foo: 'bar' },
+    ]);
+  });
+
+  it('returns a one-element array for a one-line string preceded and followed by one invalid JSON line', () => {
+    const lines = `baz
+{"foo":"bar"}
+baz2`;
+
+    const result = readJsonLines(lines);
+
+    expect(result).to.deep.equal([
+      { foo: 'bar' },
+    ]);
+  });
+
+  it('returns a two-element array for a two-line string having an invalid JSON line between', () => {
+    const lines = `{"foo":"bar"}
+baz
+{"foo2":"bar2"}
+`;
+
+    const result = readJsonLines(lines);
+
+    expect(result).to.deep.equal([
+      { foo: 'bar' },
+      { foo2: 'bar2' },
+    ]);
+  });
 });