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Sinon.JS Documentation Releases How To Works with any unit testing framework. Get Started Star Sinon.JS on Github Proudly Backed By Become a backer and support Sinon.JS with a monthly donation. Become a backer npm To install the current release ( v2.3.1 ) of Sinon: npm install sinon If you (for some reason) really want the old version of Sinon, head over to the legacy docs and do: npm install sinon@1 The following function takes a function as its argument and returns a new function. You can call the resulting function as many times as you want, but the original function will only be called once: function once(fn) { var returnValue, called = false; return function () { if (!called) { called = true; returnValue = fn.apply(this, arguments); } return returnValue; }; } Testing this fun...

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