Layer error data resolution not defined

Question

I created a Google Tag Manager data level variable and published a container. When I access the page, I get an error in the Chrome console

dataLayer is not defined

Pressing the datalayer script is in the HEAD element, and the GTM code snippet is in the Body tag.

Answer 1

If you are trying to use dataLayer, you need to make sure that it is defined before using it:

window.dataLayer = window.dataLayer || [];
window.dataLayer.push({
   'someKey': 'someValue'
})

// GTM Container here