javascript - Uncaught TypeError: Object [object DOMWindow] has no method 'replace' - Stack Overflow

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I'm studying javascript. I just want to understand why the strip2() function in the below code doesn't work, and returns an error.

<script type="text/javascript">
function strip1(str) {
  return str.replace(/^\s+|\s+$/g, "")
};
function strip2() {
  return this.replace(/^\s+|\s+$/g, "")
};

var text = ' Hello  ';
console.log(strip1(text));  // Hello
console.log(strip2(text));  // Uncaught TypeError: Object [object DOMWindow] has no method 'replace'
</script>

Thanks.

I'm studying javascript. I just want to understand why the strip2() function in the below code doesn't work, and returns an error.

<script type="text/javascript">
function strip1(str) {
  return str.replace(/^\s+|\s+$/g, "")
};
function strip2() {
  return this.replace(/^\s+|\s+$/g, "")
};

var text = ' Hello  ';
console.log(strip1(text));  // Hello
console.log(strip2(text));  // Uncaught TypeError: Object [object DOMWindow] has no method 'replace'
</script>

Thanks.

• javascript

Share Improve this question Follow edited Mar 11, 2012 at 11:30 Waynn Lue 11.4k88 gold badges5252 silver badges7777 bronze badges asked Mar 11, 2012 at 11:16 kinakomochikinakomochi 48544 gold badges88 silver badges1515 bronze badges

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4 Answers 4

Sorted by: Reset to default 4

this in that context is a pointer to the global window object, which doesn't have a replace function (since it isn't a string). So as a result, it throws an error.

The correct version would be:

console.log(strip2.call(text));

function strip2() {
  return arguments[0].replace(/^\s+|\s+$/g, "")
};

In JavaScript this always refers to the “owner” of the function we're executing, or rather, to the object that a function is a method of.

So strip2 is calling replace on the global window object.

For reference, this is an article explaining the this keyword in JavaScript: http://www.quirksmode/js/this.html

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