Add substr helper

Author: tylerturdenpants

addon/helpers/substr.js

@@ -1,11 +1,13 @@
-import { helper } from 'ember-helper';
+import Ember from 'ember';
 
-export default helper(function([value, ...rest], opts) {
+export function substr([value, ...rest], hash) {
 	if (typeof value === 'string') {
-		let start = opts.start || 0;
-		let max = opts.max;
-		return value.substr(start, max);
+		let start = hash.start || 0;
+		let length = hash.length;
+		return value.substr(start, length);
 	} else {
 		return value;
 	}
-});
+}
+
+export default Ember.Helper.helper(substr);

app/helpers/substr.js

@@ -0,0 +1 @@
+export { default, substr } from 'ember-string-helpers/helpers/substr';

tests/unit/helpers/substr-test.js

@@ -0,0 +1,51 @@
+import { substr } from '../../../helpers/substr';
+import { module, test } from 'qunit';
+
+module('Unit | Helper | substr');
+
+
+// Replace this with your real tests.
+test('number', function(assert) {
+	let result = substr([42]);
+	assert.equal(result, 42);
+});
+
+test('string', function(assert) {
+	let result = substr(['substr'], {});
+	assert.equal(result, 'substr');
+});
+
+test('empty object', function(assert) {
+	let result = substr([{}]);
+	assert.deepEqual(result, {});
+});
+
+test('object with properties', function(assert) {
+	let result = substr([{a: 1, b: 2 }]);
+	assert.deepEqual(result, {a: 1, b: 2 });
+});
+
+test('start >= length', function(assert) {
+	let result = substr(['abcdefghij'], {start: 20, length: 2});
+	assert.equal(result, '');
+});
+
+test('start <= -1', function(assert) {
+	let result = substr(['abcdefghij'], {start: -3, length: 2});
+	assert.equal(result, 'hi');
+});
+
+test('start == 1, length ommited ', function(assert) {
+	let result = substr(['abcdefghij'], {start: 1});
+	assert.equal(result, 'bcdefghij');
+});
+
+test('start == 1, length 0 ', function(assert) {
+	let result = substr(['abcdefghij'], {start: 1, length: 0});
+	assert.equal(result, '');
+});
+
+test('start == 1, length is negative ', function(assert) {
+	let result = substr(['abcdefghij'], {start: 1, length: -1});
+	assert.equal(result, '');
+});