You have an extra closing }
in your function.
var nav = document.getElementsByClassName('nav-coll');
for (var i = 0; i < button.length; i++) {
nav[i].addEventListener('click',function(){
console.log('haha');
} // <== remove this brace
}, false);
};
You really should be using something like JSHint or JSLint to help find these things. These tools integrate with many editors and IDEs, or you can just paste a code fragment into the above web sites and ask for an analysis.
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